Evolutionary déjà vu? A case of convergent evolution in an ant-plant association.

Obligatory ant-plant symbioses often appear to be single evolutionary shifts within particular ant lineages; however, convergence can be revealed once natural history observations are complemented with molecular phylogenetics. Here, we describe a remarkable example of convergent evolution in an ant-plant symbiotic system. Exclusively arboreal, Myrmelachista species can be generalized opportunists nesting in several plant species or obligately symbiotic, live-stem nesters of a narrow set of plant species. Instances of specialization within Myrmelachista are known from northern South America and throughout Middle America. In Middle America, a diverse radiation of specialists occupies understory treelets of lowland rainforests. The morphological and behavioural uniformity of specialists suggests that they form a monophyletic assemblage, diversifying after a single origin of specialization. Using ultraconserved element phylogenomics and ancestral state reconstructions, we show that shifts from opportunistic to obligately symbiotic evolved independently in South and Middle America. Furthermore, our analyses support a remarkable case of convergence within the Middle American radiation, with two independently evolved specialist clades, arising nearly simultaneously from putative opportunistic ancestors during the late Pliocene. This repeated evolution of a complex phenotype suggests similar mechanisms behind trait shifts from opportunists to specialists, generating further questions about the selective forces driving specialization.

Pheidole (Hymenoptera, Formicidae) of Middle American Wet Forest.

The ant genus Pheidole is a highly diverse lineage of ants that are dominant elements of tropical and subtropical ecosystems throughout the world. Biodiversity inventory projects in Middle American wet forests (southern Mexico to Costa Rica, lowland rainforest to high montane forest) allow an improved taxonomy of the genus in this region. An identification guide to 234 species in the region is provided, using a "bird guide" approach. Species are arranged in order of minor worker head width and scape length, and each species has a fixed layout that includes habitat and microhabitat information, standard views (minor lateral, minor face, major face), and a distribution map. The following new synonyms are proposed: biconstricta Mayr 1870 (= inermis Mayr 1870), carapuna Mann 1916 (= tristicula Wilson 2003), fimbriata Roger 1863 (= soesilae Makhan 2007), insipida Forel 1899 (= fariasana Wilson 2003, mooreorum Wilson 2003), longiscapa Forel 1901 (= cocciphaga Borgmeier 1934), plebecula Forel 1899 (= perdiligens Wilson 2003, texticeps Wilson 2003), nitidicollis Emery 1896 (= chalcoides Wilson 2003), nubicola Wilson 2003 (= cielana Wilson 2003, petrensis Wilson 2003), simonsi Wilson 2003 (= arctos Wilson 2003, gangamon Wilson 2003, thrasys Wilson 2003), striaticeps Mayr 1870 (= chloe Forel 1908), transversostriata Mayr 1887 (= scalaris Wilson 2003), vafra Santschi 1923 (= laticornis Wilson 2003). The following 57 new species are described: ajaxigibba, andersoni, angustinigra, atitlana, balatro, belonorte, besalon, bicornisculpta, brownampla, cahui, caliginosa, carinitida, corniclypeus, costaricensis, cusuco, depressinoda, eosimilis, familiaparra, fincanaranjo, hansoni, hectornitida, hitoy, huarache, imbrilis, indagarama, kasparii, kelainos, lagunculiminor, lamancha, laselvoides, lineafrons, luteagossamer, machaquila, marmor, moskitia, muralla, musacolor, musinermis, natalie, nephele, obturaculum, passivaeferox, perissothrix, platyscapa, probolonotum, rima, rogeripolita, savegre, sensipelada, sepultura, tapanti, tikal, tinamu, tsontekonwei, tuculutan, xiloa, zannia.

How ants drop out: ant abundance on tropical mountains.

In tropical wet forests, ants are a large proportion of the animal biomass, but the factors determining abundance are not well understood. We characterized ant abundance in the litter layer of 41 mature wet forest sites spread throughout Central America (Chiapas, Guatemala, Honduras, Nicaragua, and Costa Rica) and examined the impact of elevation (as a proxy for temperature) and community species richness. Sites were intentionally chosen to minimize variation in precipitation and seasonality. From sea level to 1500 m ant abundance very gradually declined, community richness declined more rapidly than abundance, and the local frequency of the locally most common species increased. These results suggest that within this elevational zone, density compensation is acting, maintaining high ant abundance as richness declines. In contrast, in sites above 1500 m, ant abundance dropped abruptly to much lower levels. Among these high montane sites, community richness explained much more of the variation in abundance than elevation, and there was no evidence of density compensation. The relative stability of abundance below 1500 m may be caused by opposing effects of temperature on productivity and metabolism. Lower temperatures may decrease productivity and thus the amount of food available for consumers, but slower metabolisms of consumers may allow maintenance of higher biomass at lower resource supply rates. Ant communities at these lower elevations may be highly interactive, the result of continuous habitat presence over geological time. High montane sites may be ephemeral in geological time, resulting in non-interactive communities dominated by historical and stochastic processes. Abundance in these sites may be determined by the number of species that manage to colonize and/or avoid extinction on mountaintops.

A review of the Central American and Caribbean species of the ant genus Eurhopalothrix Brown and Kempf, 1961 (Hymenoptera, Formicidae), with a key to New World species.

The ant genus Eurhopalothrix occurs throughout the Neotropics and Australasian tropics, where it is an inhabitant of forest leaf litter and soil. The New World species are reviewed, with an emphasis on the fauna of the MesoAmerican corridor and the Caribbean. Previously unappreciated characters of mandibular dentition and labrum shape vary dramatically among species and species groups. A total of 28 New World species are recognized, of which 14 are described as new. A key to workers of all New World species is provided. Eurhopalothrix procera is reported for the first time in the New World. The following new species are described: E. cimu Longino, sp. nov., E. circumcapillum Longino, sp. nov., E. guadeloupensis Longino, sp. nov., E. hunhau Longino, sp. nov., E. mabuya Longino, sp. nov., E. machaquila Longino, sp. nov., E. megalops Longino, sp. nov., E. ortizae Longino, sp. nov., E. oscillum Longino, sp. nov., E. semicapillum Longino, sp. nov., E. sepultura Longino, sp. nov., E. vulcan Longino, sp. nov., E. xibalba Longino, sp. nov., and E. zipacna Longino. sn. nov. Eurhopalothrix schmidti (Menozzi) is removed from synonymy with E. gravis (Mann).

A revision of the ant genus Octostruma Forel 1912 (Hymenoptera, Formicidae).

The ant genus Octostruma is restricted to the Neotropics, where it is an inhabitant of forest leaf litter and soil. The genus is reviewed, with an emphasis on the fauna of the MesoAmerican corridor. A total of 34 species are recognized, of which 19 are described as new. A key to species is provided, and the following new species are described: O. ascrobicula Long-ino, sp. nov., O. ascrobis Longino, sp. nov., O. convallis Longino, sp. nov., O. convallisur Longino, sp. nov., O. cyrtino-tum Longino, sp. nov., O. excertirugis Longino, sp. nov., O. gymnogon Longino, sp. nov., O. gymnosoma Longino, sp. nov., O. leptoceps Longino, sp. nov., O. limbifrons Longino, sp. nov., O. megabalzani Longino, sp. nov., O. montanis Longino, sp. nov., O. obtusidens Longino, sp. nov., O. pexidorsum Longino, sp. nov., O. planities Longino, sp. nov., O. schusteri Longino, sp. nov., O. triquetrilabrum Longino, sp. nov., O. triangulabrum Longino, sp. nov., and O. trithrix Longino, sp. nov. Octostruma lutzi (Wheeler) and O. amrishi (Makhan) are removed from synonymy with O. balzani (Emery). Queens are newly associated with workers for O. amrishi (Makhan), O. rugiferoides Brown & Kempf, and O. wheeleri (Mann).

New species of Central American Rhopalothrix Mayr, 1870 (Hymenoptera, Formicidae).

The ant genus Rhopalothrix is a rare inhabitant of wet forest leaf litter and soil. We propose a monophyletic R. isthmica clade that is restricted to the Neotropics, contains most of the species in the genus, and has its center of abundance and diversity in Central America. Thirteen species are recognized in the R. isthmica clade, of which eight are described as new and three are redescribed. A key to species in the R. isthmica clade is provided, and the following eight new species are described: R. andersoni Longino & Boudinot, sp. nov., R. apertor Longino & Boudinot, sp. nov., R. atitlanica Longino & Boudinot, sp. nov., R. megisthmica Longino & Boudinot, sp. nov., R. nubilosa Longino & Boudinot, sp. nov., R. subspatulata Longino & Boudinot, sp. nov., R. therion Longino & Boudinot, sp. nov., and R. triumphalis Longino & Boudinot, sp. nov.. Queens are newly associated with workers for three Central American species. New synonymy is proposed for Rhopalothrix plaumanni Brown & Kempf, 1960 = R. acutipilis Kempf, 1962, syn. nov.

Unprecedented ichneumonid parasitoid wasp diversity in tropical forests.

The megadiverse parasitoid wasp family Ichneumonidae (Hymenoptera) is classically considered an exception to the extensively studied latitudinal diversity gradient: the majority of ichneumonid species are described from temperate regions. The gradient has been hypothesized to be dependent on the biology of the wasps, but recently questions of sampling and description biases have been raised. Here, we show with primary data that the species richness of Ichneumonidae is markedly underestimated in tropical areas and that latitudinal diversity patterns in the family remain uncharacterized. We discovered a startling 177 likely undescribed orthocentrine species with relatively low sampling effort in the forests of Central America and Amazonian Ecuador, over three times the previously known orthocentrine diversity in the world's tropics. Species accumulation curves reveal that we are just beginning to unveil the true extent of tropical orthocentrine diversity. We also found evidence for cryptic species; our DNA analysis revealed additional species not easily distinguishable using morphological characteristics. The difficulty in establishing species richness patterns of Ichneumonidae probably follows from the relative lack of taxonomic expertise and the low density of ichneumonid species throughout the landscape.

Global warming, elevational range shifts, and lowland biotic attrition in the wet tropics.

Many studies suggest that global warming is driving species ranges poleward and toward higher elevations at temperate latitudes, but evidence for range shifts is scarce for the tropics, where the shallow latitudinal temperature gradient makes upslope shifts more likely than poleward shifts. Based on new data for plants and insects on an elevational transect in Costa Rica, we assess the potential for lowland biotic attrition, range-shift gaps, and mountaintop extinctions under projected warming. We conclude that tropical lowland biotas may face a level of net lowland biotic attrition without parallel at higher latitudes (where range shifts may be compensated for by species from lower latitudes) and that a high proportion of tropical species soon faces gaps between current and projected elevational ranges.

Distribución espacio-temporal de hormigas en un gradiente de luz, dentro de un sistema agroforestal de café, en Turrialba, Costa Rica

Temporal and spatial distribution of ants in a light gradient, in a coffee agroforestry system, Turrialba, Costa Rica. Shade trees are frequently present in coffee (Coffea arabica L.) agroforestry systems of Mesoamerica. These systems can harbor a rich entomofauna, including ants, which could be predators of key pests in these systems. However, the role of shade on the distribution and abundance of these ants is unknown, yet such knowledge could suggest guidelines for manipulating certain environmental conditions of their habitat, thereby achieving their conservation and increase. Therefore, we studied the effect of shade on the spatial and temporal distribution of three ant species (Solenopsis geminata, Pheidole radoszkowskii and Crematogaster curvispinosa) that may prey on the coffee berry borer, Hypothenemus hampei (Coleoptera: Scolytidae), and the mahogany shootborer, Hypsipyla grandella (Lepidoptera: Pyralidae). To do this, abundance was evaluated across a sun-shade gradient in a coffee plantation with four alternate plots (from pure sun to total shade) in Turrialba, Costa Rica. In the community that was studied 28 species of ants were collected, of which S. geminata was the dominant species (79 % of the total individuals), followed by P. radoszkowskii (16 %). S. geminata and C. curvispinosa preferred sunny areas, while P. radoszkowskii showed no defined preference. Likewise, with respect to location, S. geminata predominated in the soil, while P. radoszkowskii and C. curvispinosa predominated in coffee bushes. Rev. Biol. Trop. 55 (3-4): 943-956. Epub 2007 December, 28.

En los sistemas agroforestales de café (Coffea arabica L.) de Mesoamérica es frecuente la presencia de árboles de sombra. Estos sistemas pueden albergar una rica entomofauna, incluyendo hormigas, la cuales podrían depredar a plagas claves en dichos sistemas. Sin embargo, se desconoce el papel de la sombra sobre la distribución y abundancia de dichas hormigas, lo cual podría sugerir pautas para manipular ciertas condiciones de su hábitat y lograr su conservación e incremento. Por tanto, se estudió el efecto de la sombra sobre la distribución espacial y temporal de tres especies de hormigas (Solenopsis geminata, Pheidole radoszkowskii y Crematogaster curvispinosa) que pueden depredar a la broca del café, Hypothenemus hampei (Coleoptera: Scolytidae) y al barrenador de las meliáceas, Hypsipyla grandella. Para ello se evaluó su abundancia a través de un gradiente de sol-sombra en un cafetal con cuatro parcelas alternas (desde pleno sol hasta sombra total), en Turrialba, Costa Rica. En la comunidad estudiada se recolectaron 28 especies de hormigas, de las cuales S. geminata fue la dominante (79 % del total de individuos), seguida por P. radoszkowskii (16 %). S. geminata y C. curvispinosa prefirieron las áreas soleadas, mientras que P. radoszkowskii no mostró una preferencia definida. Asimismo, en cuanto a su ubicación, S. geminata predominó en el suelo, mientras que P. radoszkowskii y C. curvispinosa lo hicieron en los arbustos de café.

[Temporal and spatial distribution of ants in a light gradient, in a coffee agroforestry system, Turrialba, Costa Rica]. / Distribución espacio-temporal de hormigas en un gradiente de luz, dentro de un sistema agroforestal de café, en Turrialba, Costa Rica.

Shade trees are frequently present in coffee (Coffea arabica L.) agroforestry systems of Mesoamerica. These systems can harbor a rich entomofauna, including ants, which could be predators of key pests in these systems. However, the role of shade on the distribution and abundance of these ants is unknown, yet such knowledge could suggest guidelines for manipulating certain environmental conditions of their habitat, thereby achieving their conservation and increase. Therefore, we studied the effect of shade on the spatial and temporal distribution of three ant species (Solenopsis geminata, Pheidole radoszkowskii and Crematogaster curvispinosa) that may prey on the coffee berry borer, Hypothenemus hampei (Coleoptera: Scolytidae), and the mahogany shootborer, Hypsipyla grandella (Lepidoptera: Pyralidae). To do this, abundance was evaluated across a sun-shade gradient in a coffee plantation with four alternate plots (from pure sun to total shade) in Turrialba, Costa Rica. In the community that was studied 28 species of ants were collected, of which S. geminata was the dominant species (79% of the total individuals), followed by P. radoszkowskii (16 %). S. geminata and C. curvispinosa preferred sunny areas, while P. radoszkowskii showed no defined preference. Likewise, with respect to location, S. geminata predominated in the soil, while P. radoszkowskii and C. curvispinosa predominated in coffee bushes.