Manatees display diel trends in acoustic activity at two microhabitats in Belize.

Many marine mammals exhibit diel trends in vocal production, which can provide information on habitat use and behavioral activity. In Belize, Antillean manatees (Trichechus manatus manatus) commonly inhabit small depressions in the substrate or deep-water coves known as "resting holes". Determining if manatees exhibit diel temporal trends in their call production rate and call types between microhabitats can provide insights into their diurnal and nocturnal activity patterns. Here, we investigate the diel vocalization patterns of wild Antillean manatees in two adjacent resting holes off of St. George's Caye, Belize. Recordings of manatees were made using a bottom-mounted hydrophone located near a reef barrier reef for nine days in July of 2017 and ten days in January of 2018. To explore if and how manatee acoustic activity differs between sites, we compared the number of calls per hour, the number of manatee positive hours, the number of tonal and atonal sounds, and the number of boats detected across sites. A total of 370 hours of acoustic recordings were analyzed resulting in the detection of 3,262 calls. There were no significant differences in the number of manatee calls produced per hour between sites. The average number of calls produced by manatees decreased over the course of several days. The proportion of tonal calls decreased with hours after sunset and increased in boat presence. These results suggest manatees in this region may exhibit different diel activity patterns which appear to be influenced by the characteristics of the environment. These findings can support ongoing conservation and management efforts to safeguard species in Belize.

Whistle repertoire and structure reflect ecotype distinction of pantropical spotted dolphins in the Eastern Tropical Pacific.

The pantropical spotted dolphin in the Eastern Tropical Pacific (ETP) is found in two genetically and phenotypically diverged ecotypes, coastal and offshore. These habitats have distinct acoustic characteristics, which can lead to the evolution of distinct acoustic communication. Whistles are sounds widely used by dolphins to mediate species and individual recognition and social interactions. Here, we study the whistle acoustic structure and repertoire diversity of offshore and coastal pantropical spotted dolphins. Our results show that there is significantly more within- and across-group variation in whistle fundamental frequency between ecotypes than between offshore groups and between coastal groups. A Random Forest classification analysis performed with an accuracy of 83.99% and identified duration, peak and minimum frequency as the most informative variables for distinguishing between ecotypes. Overall, coastal spotted dolphins produced significantly shorter whistles that were significantly lower in frequency (peak, minimum and maximum, and start and end) than offshore dolphins. Ecotypes produced whistle repertoires that were similar in diversity, but different in contour composition, with the coastal ecotype producing more upsweep whistles than offshore dolphins. The results of this study suggest that acoustic adaptations to coastal and offshore environments could be important contributors to intraspecific variation of dolphin whistle repertoires.

Differences in the whistles of two ecotypes of bottlenose dolphins from the Gulf of California.

Intraspecific whistle variation in dolphins has been explained in the context of geographical isolation, soundscape, and social structure. Whistles of two ecotypes of bottlenose dolphins from La Paz Bay, Gulf of California, were analyzed. Both ecotypes showed similar whistle contours. However, they could be identified by contour maximum frequency which was predominantly above 15 kHz for oceanic dolphins and below 15 kHz for coastal dolphins. The different whistle frequencies of the two ecotypes could result from differences in group size and acoustic characteristics of their respective habitats, suggesting potential future passive acoustic monitoring applications.

Manatee calf call contour and acoustic structure varies by species and body size.

Vocal activity and signal characteristics of mammals are driven by several factors that result in both stability and plasticity over multiple time scales. All three extant species of manatee communicate with several calls that are especially important for maintaining contact between cows and calves. Determining if calf calls differ across manatee species will provide insights into the evolution of species-specific acoustic communication traits. We investigated the interspecific differences in the vocalizations of calves of Amazonian manatees (Trichechus inunguis) and the two subspecies of the West Indian manatee (T. manatus). Vocalizations of individual calves were recorded in rehabilitation centers in Brazil, Puerto Rico, the United States, and Mexico. The acoustic structure of calls produced by manatee calves varied between species and with body size. Amazonian manatee calves produced shorter calls with multiple notes at higher frequency while West Indian calves produced modulated calls that were lower in frequency and longer in duration. Smaller West Indian calves produced frequency modulated, hill-shaped calls that flattened with an increase in body length. Our results provide evidence for divergence in the ontogeny of vocalizations across T. manatus and T. inunguis and suggest variation in body size contributed to the evolution of differences in the characteristics of their calls.

Tour boats affect the activity patterns of bottlenose dolphins (Tursiops truncatus) in Bocas del Toro, Panama.

Bottlenose dolphins (Tursiops truncatus) of the Bocas del Toro archipelago are targeted by the largest boat-based cetacean watching operation in Panama. Tourism is concentrated in Dolphin Bay, home to a population of resident dolphins. Previous studies have shown that tour boats elicit short-term changes in dolphin behavior and communication; however, the relationship of these responses to the local population's biology and ecology is unclear. Studying the effects of tour boats on dolphin activity patterns and behavior can provide information about the biological significance of these responses. Here, we investigated the effects of tour boat activity on bottlenose dolphin activity patterns in Bocas del Toro, Panama over 10 weeks in 2014. Markov chain models were used to assess the effect of tour boats on dolphin behavioral transition probabilities in both control and impact scenarios. Effect of tour boat interactions was quantified by comparing transition probabilities of control and impact chains. Data were also used to construct dolphin activity budgets. Markov chain analysis revealed that in the presence of tour boats, dolphins were less likely to stay socializing and were more likely to begin traveling, and less likely to begin foraging while traveling. Additionally, activity budgets for foraging decreased and traveling increased as an effect of tour boat presence. These behavioral responses are likely to have energetic costs for individuals which may ultimately result in population-level impacts. Boat operator compliance with Panamanian whale watching regulations is urgently needed to minimize potential long-term impacts on this small, genetically distinct population and to ensure the future viability of the local tourism industry.

Global Diversification of Anelosimus Spiders Driven by Long-Distance Overwater Dispersal and Neogene Climate Oscillations.

Vicariance and dispersal events, combined with intricate global climatic history, have left an imprint on the spatiotemporal distribution and diversity of many organisms. Anelosimus cobweb spiders (Theridiidae), are organisms ranging in behavior from solitary to highly social, with a cosmopolitan distribution in temperate to tropical areas. Their evolutionary history and the discontinuous distribution of species richness suggest that 1) long-distance overwater dispersal and 2) climate change during the Neogene (23-2.6 Ma), may be major factors in explaining their distribution and diversification. Here, we test these hypotheses, and explicitly test if global Miocene/Pliocene climatic cooling in the last 8 Ma affected Anelosimus radiation in parallel in South America and Madagascar. To do so, we investigate the phylogeny and spatiotemporal biogeography of Anelosimus through a culmination of a 20-year comprehensive global sampling at the species level (69 species, including 84% of the known 75 species worldwide, represented by 268 individuals) using nucleotide data from seven loci (5.5 kb). Our results strongly support the monophyly of Anelosimus with an Oligocene ($\sim $30 Ma) South American origin. Major clades on other continents originate via multiple, long-distance dispersal events, of solitary or subsocial-but not social-lineages, from the Americas. These intercontinental dispersals were to Africa, Madagascar (twice), and SE Asia/Australasia. The early diversification of Anelosimus spiders coincides with a sudden thermal increase in the late Oligocene ($\sim $27-25 Ma), though no causal connection can be made. Our results, however, strongly support the hypothesis that global Neogene climatic cooling in the last 8 Ma drove Anelosimus radiation in parallel in South America and Madagascar, offering a rare empirical evidence for diversification of a socially diverse group driven by an interplay between long-distance dispersal and global Neogene climatic changes. [Cobweb spiders; diversification; global biogeography; long-distance dispersal; molecular phylogenetics; neogene climate changes; sociality; vicariance.].

Foraging habits and levels of mercury in a resident population of bottlenose dolphins (Tursiops truncatus) in Bocas del Toro Archipelago, Caribbean Sea, Panama.

A small and genetically isolated bottlenose dolphin (Tursiops truncatus) population resides year-round in the Bocas del Toro Archipelago-Panama (BDT). Photo-identification and genetic data showed that this dolphin population is highly phylopatric and is formed exclusively by individuals of the "inshore form". This study aimed to investigate the trophic ecology and mercury concentrations of bottlenose dolphins in BDT to assess their coastal habits. We collected muscle samples (n = 175) of 11 potential fish prey species, and skin samples from free-ranging dolphins in BDT (n = 37) and La Guajira-Colombia (n = 7) to compare isotopic niche width. Results showed that BDT dolphins have a coastal feeding habit, belong to the "inshore form" (δ13C = -13.05 ±â€¯1.89‰), and have low mercury concentrations (mean = 1637 ±â€¯1387 ng g-1dw). However, this element is biomagnified in the BDT food chain, showing a marginal dolphins health risk (RQ = 1.00). We call for a monitoring pollutant program and conservation strategies aimed to protect the dolphin population at BDT.

The newly described Araguaian river dolphins, Inia araguaiaensis (Cetartiodactyla, Iniidae), produce a diverse repertoire of acoustic signals.

The recent discovery of the Araguaian river dolphin (Inia araguaiaensis) highlights how little we know about the diversity and biology of river dolphins. In this study, we described the acoustic repertoire of this newly discovered species in concert with their behaviour. We analysed frequency contours of 727 signals (sampled at 10 ms temporal resolution). These contours were analyzed using an adaptive resonance theory neural network combined with dynamic time-warping (ARTwarp). Using a critical similarity value of 96%, frequency contours were categorized into 237 sound-types. The most common types were emitted when calves were present suggesting a key role in mother-calf communication. Our findings show that the acoustic repertoire of river dolphins is far from simple. Furthermore, the calls described here are similar in acoustic structure to those produced by social delphinids, such as orcas and pilot whales. Uncovering the context in which these signals are produced may help understand the social structure of this species and contribute to our understanding of the evolution of acoustic communication in whales.

Song structure and singing activity of two separate humpback whales populations wintering off the coast of Caño Island in Costa Rica.

Central American (CA) and Breeding Stock-G (BSG) humpback whales are known to winter off Caño Island, Costa Rica at different times of the year. To study their singing behavior, autonomous underwater recorders were used to record the whales. Song detection for BSG whales was higher than CA whales, and song structure was distinct for each population. No strong evidence for cross-equatorial connectivity was found. This study provides the first humpback whale song reference for both populations in Costa Rica, which can help advance understanding of CA and BSG whale song rate of change and connectivity with other wintering areas.

High genetic structure and low mitochondrial diversity in bottlenose dolphins of the Archipelago of Bocas del Toro, Panama: A population at risk?

The current conservation status of the bottlenose dolphin (Tursiops truncatus) under the IUCN is 'least concern'. However, in the Caribbean, small and localized populations of the 'inshore form' may be at higher risk of extinction than the 'worldwide distributed form' due to a combination of factors including small population size, high site fidelity, genetic isolation, and range overlap with human activities. Here, we study the population genetic structure of bottlenose dolphins from the Archipelago of Bocas del Toro in Panama. This is a small population characterized by high site fidelity and is currently heavily-impacted by the local dolphin-watching industry. We collected skin tissue samples from 25 dolphins to study the genetic diversity and structure of this population. We amplified a portion of the mitochondrial Control Region (mtDNA-CR) and nine microsatellite loci. The mtDNA-CR analyses revealed that dolphins in Bocas del Toro belong to the 'inshore form', grouped with the Bahamas-Colombia-Cuba-Mexico population unit. They also possess a unique haplotype new for the Caribbean. The microsatellite data indicated that the Bocas del Toro dolphin population is highly structured, likely due to restricted movement patterns. Previous abundance estimates obtained with mark-recapture methods reported a small population of 80 dolphins (95% CI = 72-87), which is similar to the contemporary effective population size estimated in this study (Ne = 73 individuals; CI = 18.0 - ∞; 0.05). The combination of small population size, high degree of genetic isolation, and intense daily interactions with dolphin-watching boats puts the Bocas del Toro dolphin to at high risk of extinction. Despite national guidelines to regulate the dolphin-watching industry in Bocas del Toro and ongoing educational programs for tour operators, only in 2012 seven animals have died due to boat collisions. Our results suggest that the conservation status of bottlenose dolphins in Bocas del Toro should be elevated to 'endangered' at the national level, as a precautionary measure while population and viability estimates are conducted.

A revised and dated phylogeny of cobweb spiders (Araneae, Araneoidea, Theridiidae): A predatory Cretaceous lineage diversifying in the era of the ants (Hymenoptera, Formicidae).

Cobweb spiders (Theridiidae) are highly diverse from the perspective of species richness, morphological diversity, variety of web architecture, and behavioral repertoires. The family includes over 50% of social spiders, a behavioral rarity among the order, and members of the family are furthermore the subject of research on venom, silk biomechanics, kleptoparasitism and web building, among other traits. Theridiidae is one of the most abundant groups of spiders, and thus key insect predators in many different ecosystems and is among relatively few spider families that show high degree of myrmecophagy. Modern comparative studies on all these fronts are best buttressed on a phylogenetic foundation. Our goal here is to offer a revised, dated, phylogenetic hypothesis for the family by summarizing previously published data from multiple molecular and morphological studies through data-mining, and adding novel data from several genera. We also test the hypothesis that the origin and diversification of cobweb spiders coincides with that of ants on which many species specialize as prey. The new phylogeny is largely congruent with prior studies and current taxonomy and should provide a useful tool for theridiid classification and for comparative analyses. Nevertheless, we also highlight the limitations of currently available data-the state of the art in Theridiidae phylogenetics-offering weak support for most of the deeper nodes in the phylogeny. Thus the need is clear for modern phylogenomic approaches to obtain a more solid understanding, especially of relationships among subfamilies. We recover the monophyly of currently recognized theridiid subfamilies with the exception of some enigmatic 'pholcommatines' (Styposis, Phoroncidia) and putative 'hadrotarsines' (Audifia, Tekellina) whose placement is uncertain in our analyses. Theridiidae dates back some 100 mya to the Cretaceous, a period of diversification in flowering plants and many groups of insects, including ants. The origin of cobweb spiders, and hence the cobweb-a speciallized trap for pedestrian prey-coincides with a major diversification shift in ants. The family becomes abundant in fossil record 50-40 mya as ants also diversify and reach dominance and contemporary patterns of abundances of theridiids and ants show the same trends, with increasing relative abundance towards the equator and at lower altitudes. We find that among orbiculariae, lineages that specialize on ant prey are non-randomly clustered within Theridiidae. Given these findings we hypothesize that the origin of the gumfoot web was a stepping stone that facilitated the capture of ants and resulted in specialized myrmecophagy in a number of 'basal' theridiids. We also document a subsequent loss in myrmecophagy, and associated increase in speciation rates, as 'recent' theridiid groups evolve diverse web forms and many return to the capture of aerial prey.

Islands within islands: Diversification of tailless whip spiders (Amblypygi, Phrynus) in Caribbean caves.

Islands have played a key role in understanding species formation ever since Darwin's work on the Galapagos and Wallace's work in the Malay Archipelago. Like oceanic islands, habitat 'islands', such as mountaintops and caves similarly may drive diversification. Here we examine patterns of diversification in the tailless whip spider genus Phrynus Larmarck, 1809 (Amblypygida: Phrynidae) a system that shows evidence of diversification under the influence of 'islands within islands'. We estimate phylogeographic history and measure genetic diversity among representatives of three nominal Phrynus species from epigean and cave systems of Puerto Rico and nearby islands. Data from five loci (mitochondrial 12S, 16S, Cox1; nuclear H3, 28S) were used to generate phylogenetic hypotheses and to assess species monophyly and phylogeographic relationships. Genetic divergences and population limits were estimated and assessed using the Geneious barcoding plugin and the genealogical sorting index. We find that mtDNA sequence divergences within each of the three Phrynus species range between 15% and 20%. Genetic divergence is structured at three spatial scales: among islands in a manner consistent with the GAARlandia hypothesis, among bedrock formations within Puerto Rico, and among caves within these formations. Every isolated cave system contains a unique mtDNA genetic lineage of Phrynus, with divergence among cave systems far exceeding that within. In some localities epigean specimens nest among cave taxa, in others caves are monophyletic. Remarkably, clades that show up to 20% mtDNA sequence divergence show little or no variation in the nuclear markers. We interpret this pattern as resulting from extreme conservation of our nuclear markers rather than male sex-biased dispersal, based on high conservation of 28S and H3 between our individuals and other amblypygid genera that are restricted to Africa. While this study includes but a tiny fraction of Caribbean caves, our findings suggest Phrynus may be much more diverse than hitherto thought, at least in terms of mtDNA diversity, and that the arthropod fauna of caves may represent a dimension of biodiversity that is yet to be discovered in the Caribbean biodiversity hotspot.

A trade-off between precopulatory and postcopulatory trait investment in male cetaceans.

Mating with multiple partners is common across species, and understanding how individual males secure fertilization in the face of competition remains a fundamental goal of evolutionary biology. Game theory stipulates that males have a fixed budget for reproduction that can lead to a trade-off between investment in precopulatory traits such as body size, armaments, and ornaments, and postcopulatory traits such as testis size and spermatogenic efficiency. Recent theoretical and empirical studies have shown that if males can monopolize access to multiple females, they will invest disproportionately in precopulatory traits and less in postcopulatory traits. Using phylogenetically controlled comparative methods, we demonstrate that across 58 cetacean species with the most prominent sexual dimorphism in size, shape, teeth, tusks, and singing invest significantly less in relative testes mass. In support of theoretical predictions, these species tend to show evidence of male contests, suggesting there is opportunity for winners to monopolize access to multiple females. Our approach provides a robust dataset with which to make predictions about male mating strategies for the many cetacean species for which adequate behavioral observations do not exist.

Mammals from 'down under': a multi-gene species-level phylogeny of marsupial mammals (Mammalia, Metatheria).

Marsupials or metatherians are a group of mammals that are distinct in giving birth to young at early stages of development and in having a prolonged investment in lactation. The group consists of nearly 350 extant species, including kangaroos, koala, possums, and their relatives. Marsupials are an old lineage thought to have diverged from early therian mammals some 160 million years ago in the Jurassic, and have a remarkable evolutionary and biogeographical history, with extant species restricted to the Americas, mostly South America, and to Australasia. Although the group has been the subject of decades of phylogenetic research, the marsupial tree of life remains controversial, with most studies focusing on only a fraction of the species diversity within the infraclass. Here we present the first Methaterian species-level phylogeny to include 80% of the extant marsupial species and five nuclear and five mitochondrial markers obtained from Genbank and a recently published retroposon matrix. Our primary goal is to provide a summary phylogeny that will serve as a tool for comparative research. We evaluate the extent to which the phylogeny recovers current phylogenetic knowledge based on the recovery of "benchmark clades" from prior studies-unambiguously supported key clades and undisputed traditional taxonomic groups. The Bayesian phylogenetic analyses recovered nearly all benchmark clades but failed to find support for the suborder Phalagiformes. The most significant difference with previous published topologies is the support for Australidelphia as a group containing Microbiotheriidae, nested within American marsupials. However, a likelihood ratio test shows that alternative topologies with monophyletic Australidelphia and Ameridelphia are not significantly different than the preferred tree. Although further data are needed to solidify understanding of Methateria phylogeny, the new phylogenetic hypothesis provided here offers a well resolved and detailed tool for comparative analyses, covering the majority of the known species richness of the group.

Multiple origins of subsociality in crab spiders (Thomisidae).

Determining factors that facilitate the transition from a solitary to a social lifestyle is a major challenge in evolutionary biology, especially in taxa that are usually aggressive towards conspecifics. Most spiders live solitarily and few species are known to be social. Nevertheless, sociality has evolved multiple times across several families and nearly all studied social lineages have originated from a periodically social (subsocial) ancestor. Group-living crab spiders (Thomisidae) are exclusively found in Australia and differ from most other social spiders because they lack a communal capture web. Three of the group-living species were placed in the genus Diaea and another in the genus Xysticus. Most Australian thomisids are, however, difficult to identify as most descriptions are old and of poor quality, and the genera Diaea and Xysticus may not correspond to monophyletic groups. Here, we clarify the phylogenetic relationships of the four group-living Australian thomisids and conclude that amongst these subsociality has evolved two to three times independently. The subsocial Xysticus bimaculatus is not closely related to any of the social Diaea and an independent origin of subsociality is likely in this case. The presented data indicates that within Diaea two origins of subsociality are possible. Our results help to understand the evolution of sociality in thomisids and support the hypothesis that permanent sociality in spiders has evolved multiple times relatively recently from subsocial ancestors.

Dolphin changes in whistle structure with watercraft activity depends on their behavioral state.

Dolphins rely on whistles to identify each other and to receive and convey information about their environment. Although capable of adjusting these signals with changing environments, there is little information on how dolphins acoustically respond to different watercraft activities and if this response depends on dolphin behavioral state. Bottlenose dolphin whistles were recorded in the presence of research and dolphin-watching boats. Dolphins emitted lower frequency and longer whistles when interacting with dolphin-watching boats, particularly during foraging activities. This study suggests that dolphin-watching boat traffic significantly hinders dolphin communication during important behavioral states.

Guyana dolphins (Sotalia guianensis) from Costa Rica emit whistles that vary with surface behaviors.

Guyana dolphins show remarkable intraspecific whistle variation. This variation has been largely explained in terms of distance among populations; however, other factors such as behavior may also be important. A broadband recording system recorded the whistles of Guyana dolphins under three behavioral states. A discriminant analysis found that during social and travel events, dolphins emit whistles with high delta and minimum frequency, respectively. Whistle duration was also important in discriminating behaviors. This study indicates that behavior is an important factor contributing to whistle variation of Guyana dolphins. Understanding how dolphin whistles vary with behavioral context will advance our understanding of dolphin communication and enable appropriate comparative studies.

Small-scale estimation of relative abundance for the coastal spotted dolphins (Stenella attenuata) in Costa Rica: the effect of habitat and seasonality / Estimación a pequeña escala de la abundancia relativa del delfín manchado costero (Stenella attenuata) en Costa Rica: el efecto del hábitat y la estacionalidad

The coastal spotted dolphin (Stenella attenuata graffmani) is one of the most common species of dolphin in inshore Pacific waters of Costa Rica. We conducted surveys in protected waters of the Papagayo Gulf, Costa Rica, to determine relative abundance of dolphins in relation to environmental variables. We used Generalized Additive Models to investigate the influence of a particular set of environmental factors and determine inter-annual trends in relative abundance. School sizes ranged from 1 to 50 individuals ( mean 9.95, SD=10.28). The number of dolphins increased linearly with water depth and transparency, and non-linearly with the dissolved oxygen concentration. High variability in the relative abundance occurred during the dry season (January-April). A previous study on this population found that high number of groups are involved in foraging activities during the dry season. Seasonal changes in relative abundance probably are associated with food availability, a variable that we did not measure. Understanding local resident populations may have important implications for conservation and management strategies. Large-scale studies may overlook variables affecting the abundance of local resident populations that may be detected with studies on a smaller scale such as this one.

El delfín manchado costero (Stenella attenuata graffmani) es una de las especies de delfines mas comunes de las aguas costeras del Pacifico de Costa Rica. En este estudio realizamos muestreos dentro de las aguas protegidas del Golfo de Papagayo para determinar su abundancia relativa en relación a características físico-químicas de su hábitat. Usamos modelos aditivos generalizados para investigar la influencia de un juego de variables ambientales y determinar tendencias inter-anuales en la abundancia relativa. El tamaño de los grupos varió de 1 a 50 individuos (promedio 9.95, SD=10.28). La cantidad de delfines aumentó linealmente con la profundidad y claridad del agua, y de forma no lineal con el oxígeno disuelto. Durante la época seca (enero-abril) encontramos la mayor variabilidad en la abundancia relativa. Un estudio anterior sugiere que una cantidad importante de delfines se alimenta aquí en la época seca. Ello sugiere que los cambios estacionales en la abundancia relativa de delfines manchados costeros podría estar asociada con la disponibilidad de alimento, una variable que no medimos pero que podría explicar la variación observada debido a la naturaleza productiva estacional del área. Los estudios de poblaciones locales y residentes pueden tener un mayor impacto en estrategias de conservación y manejo. Por lo general, los estudios a mayor escala geográfica pueden pasar por alto variables importantes que afectan la abundancia local de poblaciones residentes, las cuales pueden ser detectadas en estudios de menor escala como el presente.

Expensive Brains: "Brainy" Rodents have Higher Metabolic Rate.

Brains are the centers of the nervous system of animals, controlling the organ systems of the body and coordinating responses to changes in the ecological and social environment. The evolution of traits that correlate with cognitive ability, such as relative brain size is thus of broad interest. Brain mass relative to body mass (BM) varies among mammals, and diverse factors have been proposed to explain this variation. A recent study provided evidence that energetics play an important role in brain evolution (Isler and van Schaik, 2006). Using composite phylogenies and data drawn from multiple sources, these authors showed that basal metabolic rate (BMR) correlates with brain mass across mammals. However, no such relationship was found within rodents. Here we re-examined the relationship between BMR and brain mass within Rodentia using a novel species-level phylogeny. Our results are sensitive to parameter evaluation; in particular how species mass is estimated. We detect no pattern when applying an approach used by previous studies, where each species BM is represented by two different numbers, one being the individual that happened to be used for BMR estimates of that species. However, this approach may compromise the analysis. When using a single value of BM for each species, whether representing a single individual, or available species mean, our findings provide evidence that brain mass (independent of BM) and BMR are correlated. These findings are thus consistent with the hypothesis that large brains evolve when the payoff for increased brain mass is greater than the energetic cost they incur.

Phylogenetic analysis of conservation priorities for aquatic mammals and their terrestrial relatives, with a comparison of methods.

BACKGROUND: Habitat loss and overexploitation are among the primary factors threatening populations of many mammal species. Recently, aquatic mammals have been highlighted as particularly vulnerable. Here we test (1) if aquatic mammals emerge as more phylogenetically urgent conservation priorities than their terrestrial relatives, and (2) if high priority species are receiving sufficient conservation effort. We also compare results among some phylogenetic conservation methods. METHODOLOGY/PRINCIPAL FINDINGS: A phylogenetic analysis of conservation priorities for all 620 species of Cetartiodactyla and Carnivora, including most aquatic mammals. Conservation priority ranking of aquatic versus terrestrial species is approximately proportional to their diversity. However, nearly all obligated freshwater cetartiodactylans are among the top conservation priority species. Further, ∼74% and 40% of fully aquatic cetartiodactylans and carnivores, respectively, are either threatened or data deficient, more so than their terrestrial relatives. Strikingly, only 3% of all 'high priority' species are thought to be stable. An overwhelming 97% of these species thus either show decreasing population trends (87%) or are insufficiently known (10%). Furthermore, a disproportional number of highly evolutionarily distinct species are experiencing population decline, thus, such species should be closely monitored even if not currently threatened. Comparison among methods reveals that exact species ranking differs considerably among methods, nevertheless, most top priority species consistently rank high under any method. While we here favor one approach, we also suggest that a consensus approach may be useful when methods disagree. CONCLUSIONS/SIGNIFICANCE: These results reinforce prior findings, suggesting there is an urgent need to gather basic conservation data for aquatic mammals, and special conservation focus is needed on those confined to freshwater. That evolutionarily distinct--and thus 'biodiverse'--species are faring relatively poorly is alarming and requires further study. Our results offer a detailed guide to phylogeny-based conservation prioritization for these two orders.