Phylogeography and evolutionary history of the Panamic Clingfish Gobiesox adustus in the Tropical Eastern Pacific.

The Panamic Clingfish Gobiesox adustus is widely distributed in the Tropical Eastern Pacific (TEP), from the central Gulf of California, Mexico to Ecuador, including the oceanic Revillagigedo Archipelago, and Isla del Coco. This cryptobenthic species is restricted to very shallow rocky-reef habitats. Here, we used one mitochondrial and three nuclear DNA markers from 155 individuals collected across the distribution range of the species in order to evaluate if geographically structured populations exist and to elucidate its evolutionary history. Phylogenetic analyses recovered a monophyletic group, with four well-supported, allopatric subgroups. Each subgroup corresponded to one of the following well-known biogeographic regions/provinces: 1) the Revillagigedo Archipelago, 2) the Cortez + Mexican provinces (Mexico), 3) the Panamic province (from El Salvador to Ecuador), and 4) Isla del Coco. A molecular-clock analysis showed a mean date for the divergence between clade I (the Revillagigedos and Cortez + Mexican provinces) and clade II (Panamic province and Isla del Coco) in the Pliocene, at ca. 5.33 Mya. Within clade I, the segregation between the Revillagigedos and Cortez + Mexican province populations was dated at ca. 1.18 Mya, during the Pleistocene. Within clade II, the segregation between samples of Isla del Coco and the Panamic province samples was dated at ca. 0.77 Mya, during the Pleistocene. The species tree, Bayesian species delimitation tests (BPP and STACEY), the ΦST, AMOVA, and the substantial genetic distances that exist between those four subgroups, indicate that they are independent evolutionary units. These cladogenetic events seem to be related to habitat discontinuities, and oceanographic and geological processes that produce barriers to gene flow for G. adustus, effects of which are enhanced by the intrinsic ecological characteristics of this species.

Environmental heterogeneity and not vicariant biogeographic barriers generate community-wide population structure in desert-adapted snakes.

Genetic structure can be influenced by local adaptation to environmental heterogeneity and biogeographic barriers, resulting in discrete population clusters. Geographic distance among populations, however, can result in continuous clines of genetic divergence that appear as structured populations. Here, we evaluate the relevant importance of these three factors over a landscape characterized by environmental heterogeneity and the presence of a hypothesized biogeographic barrier in producing population genetic structure within 13 codistributed snake species using a genomic data set. We demonstrate that geographic distance and environmental heterogeneity across western North America contribute to population genomic divergence. Surprisingly, landscape features long thought to contribute to biogeographic barriers play little role in divergence community wide. Our results suggest that isolation by environment is the most important contributor to genomic divergence. Furthermore, we show that models of population clustering that incorporate spatial information consistently outperform nonspatial models, demonstrating the importance of considering geographic distances in population clustering. We argue that environmental and geographic distances as drivers of community-wide divergence should be explored before assuming the role of biogeographic barriers.

Rediscovery of an endemic vertebrate from the remote Islas Revillagigedo in the eastern Pacific Ocean: the Clarión nightsnake lost and found.

Vertebrates are currently going extinct at an alarming rate, largely because of habitat loss, global warming, infectious diseases, and human introductions. Island ecosystems are particularly vulnerable to invasive species and other ecological disturbances. Properly documenting historic and current species distributions is critical for quantifying extinction events. Museum specimens, field notes, and other archived materials from historical expeditions are essential for documenting recent changes in biodiversity. The Islas Revillagigedo are a remote group of four islands, 700-1100 km off the western coast of mainland México. The islands are home to many endemic plants and animals recognized at the specific- and subspecific-levels, several of which are currently threatened or have already gone extinct. Here, we recount the initial discovery of an endemic snake Hypsiglena ochrorhyncha unaocularus Tanner on Isla Clarión, the later dismissal of its existence, its absence from decades of field surveys, our recent rediscovery, and recognition of it as a distinct species. We collected two novel complete mitochondrial (mt) DNA genomes and up to 2800 base-pairs of mtDNA from several other individuals, aligned these with previously published mt-genome data from samples throughout the range of Hypsiglena, and conducted phylogenetic analyses to infer the biogeographic origin and taxonomic status of this population. We found the Isla Clarión population to be most closely related to populations in the Sonora-Sinaloa state border area of mainland México and Isla Santa Catalina, in the Gulf of California. Based on genetics, morphology, and geographic distributions, we also recognize these two other lineages as distinct species. Our study shows the importance of museum specimens, field notes, and careful surveys to accurately document biodiversity and brings these island endemics (Clarión and Santa Catalina nightsnakes) and mainland population near the Sonora-Sinaloa state border to the attention of conservation biologists currently monitoring biodiversity in these fragile subtropical ecosystems.

Diversity and phylogenetic relationships of hemosporidian parasites in birds of Socorro Island, México, and their role in the re-introduction of the Socorro dove (Zenaida graysoni).

The Socorro dove Zenaida graysoni , endemic to Socorro Island, was last reported in the wild in 1972. Fortunately, the species has been propagated in zoos in Europe and the United States, and plans are under way to re-introduce it to its native habitat. This will be the first known attempt to return a bird species extinct in the wild to its ancestral island. In order to assess the disease threats the Socorro dove may face, the avifauna of Socorro Island, with a specific focus on Socorro ground doves Columbina passerina socorroensis and mourning doves Zenaida macroura , as well as Socorro doves in captivity, were screened for blood parasites of the genera Plasmodium , Haemoproteus, Leucocytozoon, and Trypanosoma spp. We found Haemoproteus spp. in 17 (74%) of 23 Socorro ground doves, 23 (92%) of 25 mourning doves, and 3 (14%) of 21 northern mockingbirds; none of the other bird species showed infections. Here, we report the phylogenetic analysis of 19 distinct lineages of Haemoproteus spp. detected in birds of Socorro Island and compare their evolutionary relationships to parasites detected in the avifauna of the Galápagos Islands, continental Latin America, and Europe. Microscopic examination revealed 1 mourning dove infected with Plasmodium ( Haemamoeba ), thus underscoring the importance of using both PCR and microscopy when analyzing avian blood samples for hemosporidian parasites. The study confirms that the Socorro dove will most likely be exposed to Haemoproteus spp. that currently infect mourning doves and Socorro ground doves of Socorro Island. A monitoring program for both birds and vectors should be implemented to establish the prevalence of Plasmodium sp. and as a necessary conservation measure for critically endangered birds on the island.

Two new Haemoproteus species (Haemosporida: Haemoproteidae) from columbiform birds.

Here we describe Haemoproteus (Haemoproteus) multivolutinus n. sp. from a tambourine dove (Turtur timpanistria) of Uganda and Haemoproteus (Haemoproteus) paramultipigmentatus n. sp. (Haemosporida, Haemoproteidae) from the Socorro common ground dove (Columbina passerina socorroensis) of Socorro Island, Mexico. These parasites are described based on the morphology of their blood stages and segments of the mitochondrial cytochrome b gene that can be used for molecular identification and diagnosis of these species. Gametocytes of H. multivolutinus possess rod-like pigment granules and are evenly packed with volutin, which masks pigment granules and darkly stains both macro- and microgametocytes in the early stages of their development. Based on these 2 characters, H. multivolutinus can be readily distinguished from other species of hemoproteids parasitizing columbiform (Columbiformes) birds. Haemoproteus paramultipigmentatus resembles Haemoproteus multipigmentatus; it can be distinguished from the latter parasite primarily due to the broadly ovoid shape of its young gametocytes and significantly fewer pigment granules in its fully developed gametocytes. We provide illustrations of blood stages of the new species, and phylogenetic analyses identify DNA lineages closely related to these parasites. Cytochrome b lineages of Haemoproteus multivolutinus and H. paramultipigmentatus cluster with hippoboscid-transmitted lineages of hemoproteids; thus these parasites likely belong to the subgenus Haemoproteus. We emphasize the importance of using cytochrome b sequences in conjunction with thorough microscopic descriptions to facilitate future identification of these and other avian hemosporidian species.

Implications of Plasmodium parasite infected mosquitoes on an insular avifauna: the case of Socorro Island, México.

Avian malaria (Plasmodium spp.) has been implicated in the decline of avian populations in the Hawaiian Islands and it is generally agreed that geographically isolated and immunologically naïve bird populations are particularly vulnerable to the pathogenic effects of invasive malaria parasites. In order to assess the potential disease risk of malaria to the avifauna of Socorro Island, México, we surveyed for Plasmodium isolates from 1,300 resident field-caught mosquitoes. Most of them were identified as Aedes (Ochlerotatus) taeniorhynchus (Wiedemann, 1821), which were abundant in the salt marshes. We also collected Culex quinquefasciatus Say, 1823 close to human dwellings. Mitochondrial ND5 and COII gene sequences of Ae. taeniorhynchus were analyzed and compared to corresponding sequences of mosquitoes of the Galápagos Islands, Latin America, and the North American mainland. Aedes lineages from Socorro Island clustered most closely with a lineage from the continental U.S. Plasmodium spp. DNA was isolated from both species of mosquitoes. From 38 positive pools, we isolated 11 distinct mitochondrial Cytb lineages of Plasmodium spp. Seven of the Plasmodium lineages represent previously documented avian infective strains while four were new lineages. Our results confirm a potential risk for the spread of avian malaria and underscore the need to monitor both the mosquito and avian populations as a necessary conservation measure to protect endangered bird species on Socorro Island.