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Sunday, March 11th, 2018
| Time | Event | ||||||||||
| 6:09p | [Arachnida • 2018] Repeated Diversification of Ecomorphs in Hawaiian Stick Spiders, Ariamnes spp.
Highlights: • Hawaiian stick spiders show adaptive radiation with repeated evolution of ecomorphs• This phenomenon is found in only a few adaptive radiations of island insectivores • Camouflage against a finite set of predators and wandering habit play key roles • Limited pathways for the development of color contribute to deterministic evolution Summary Insular adaptive radiations in which repeated bouts of diversification lead to phenotypically similar sets of taxa serve to highlight predictability in the evolutionary process. However, examples of such replicated events are rare. Cross-clade comparisons of adaptive radiations are much needed to determine whether similar ecological opportunities can lead to the same outcomes. Here, we report a heretofore uncovered adaptive radiation of Hawaiian stick spiders (Theridiidae, Ariamnes) in which different species exhibit a set of discrete ecomorphs associated with different microhabitats. The three primary ecomorphs (gold, dark, and matte white) generally co-occur in native forest habitats. Phylogenetic reconstruction mapped onto the well-known chronosequence of the Hawaiian Islands shows both that this lineage colonized the islands only once and relatively recently (2–3 mya, when Kauai and Oahu were the only high islands in the archipelago) and that the distinct ecomorphs evolved independently multiple times following colonization of new islands. This parallel evolution of ecomorphs matches that of “spiny-leg” long-jawed spiders (Tetragnathidae, Tetragnatha), also in Hawaii. Both lineages are free living, and both have related lineages in the Hawaiian Islands that show quite different patterns of diversification with no evidence of deterministic evolution. We argue that repeated evolution of ecomorphs results from a rugged adaptive landscape, with the few peaks associated with camouflage for these free-living taxa against the markedly low diversity of predators on isolated islands. These features, coupled with a limited genetic toolbox and reduced dispersal between islands, appear to be common to situations of repeated evolution of ecomorphs.
Rosemary G. Gillespie, Suresh P. Benjamin, Michael S. Brewer, Malia Ana J. Rivera and George K. Roderick. 2018. Repeated Diversification of Ecomorphs in Hawaiian Stick Spiders. Current Biology. DOI: 10.1016/j.cub.2018.01.083 How brightly colored spiders evolved on Hawaii again and again... and again http://phy.so/439734740 @physorg_com  | ||||||||||
| 6:15p | [Herpetology • 2018] Leptobrachella Smith 1928 • Large-scale Phylogenetic Analyses provide insights into Unrecognized Diversity and Historical Biogeography of Asian Leaf-litter Frogs, Genus Leptolalax (Anura: Megophryidae)
Highlights • The most comprehensive and robust phylogeny for Leptolalax to date is presented. • The presence of many putative undescribed species in Leptolalax is detected. • Diversification in the group is complex, involving a high degree of sympatry and prevalence of microendemic species. • The genus appears to have originated in Sundaland, consistent with an “upstream” hypothesis of colonization. • A taxonomic revision of the genera Leptolalax and Leptobrachella is proposed. Abstract Southeast Asia and southern China (SEA-SC) harbor a highly diverse and endemic flora and fauna that is under increasing threat. An understanding of the biogeographical history and drivers of this diversity is lacking, especially in some of the most diverse and threatened groups. The Asian leaf-litter frog genus Leptolalax Dubois 1980 is a forest-dependent genus distributed throughout SEA-SC, making it an ideal study group to examine specific biogeographic hypotheses. In addition, the diversity of this genus remains poorly understood, and the phylogenetic relationships among species of Leptolalax and closely related Leptobrachella Smith 1928 remain unclear. Herein, we evaluate species-level diversity based on 48 of the 53 described species from throughout the distribution of Leptolalax. Molecular analyses reveal many undescribed species, mostly in southern China and Indochina. Our well-resolved phylogeny based on multiple nuclear DNA markers shows that Leptolalax is not monophyletic with respect to Leptobrachella and, thus, we assign the former to being a junior synonym of the latter. Similarly, analyses reject monophyly of the two subgenera of Leptolalax. The diversification pattern of the group is complex, involving a high degree of sympatry and prevalence of microendemic species. Northern Sundaland (Borneo) and eastern Indochina (Vietnam) appear to have played pivotal roles as geographical centers of diversification, and paleoclimatic changes and tectonic movements seem to have driven the major divergence of clades. Analyses fail to reject an “upstream” colonization hypothesis, and, thus, the genus appears to have originated in Sundaland and then colonized mainland Asia. Our results reveal that both vicariance and dispersal are responsible for current distribution patterns in the genus. Keywords: Species delimitation; Biogeography; Source-sink dynamics; Taxonomy; Leptolalax; Leptobrachella    "Leptolalax Dubois 1980 to being a junior synonym of Leptobrachella Smith 1928" Conclusions: This study provides valuable insights into the diversity, phylogeny and biogeography of Asian leaf-litter frogs formerly in the genus Leptolalax, using broad sampling and a multilocus approach. Our results reveal multiple, geographically structured, clades within Leptolalax, and for the first time, we produce convincing evidence that Leptolalax is paraphyletic, as Leptobrachella is recovered nesting within the genus. Analyses reject the earlier proposed recognition of two subgenera of Leptolalax. An underestimation of species diversity occurs in the group, which suggests a high degree of localized diversification and microendemism. Our spatiotemporal analysis suggests that the past climatic and tectonic events have likely contributed to the current distribution pattern of Leptobrachella. A synthesis of 20 diversification patterns for a wide range of other genera endemic to SEA-SC will yield a more comprehensive picture of the drivers of speciation in this highly diverse but complicated region. Jin-Min Chen, Nikolay A. Poyarkov Jr., Chatmongkon Suwannapoom, Amy Lathrop, Yun-He Wu, Wei-Wei Zhou, Zhi-Yong Yuan, Jie-Qiong Jin, HongMan Chen, He-Qun Liu, Truong Quang Nguyen, Sang Ngoc Nguyen, Tang Van Duong, Koshiro Eto, Kanto Nishikawa, Masafumi Matsui, Nikolai L. Orlov, Bryan L. Stuart, Rafe M. Brown, Jodi J.L. Rowley, Robert W. Murphy, YingYong Wang, Jing Che. 2018. Large-scale Phylogenetic Analyses provide insights into Unrecognized Diversity and Historical Biogeography of Asian Leaf-litter Frogs, Genus Leptolalax (Anura: Megophryidae). Molecular Phylogenetics and Evolution. In Press. DOI: 10.1016/j.ympev.2018.02.020 |
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