Biology subjects

Galen, S. C.

Publications and source records attributed to Galen, S. C..

3 recordsLinked to original sources

bioRxiv2018

Deeply conserved susceptibility in a multi-host, multi-parasite system

Variation in susceptibility is ubiquitous in multi-host, multi-parasite assemblages, and can have profound implications for ecology and evolution. The extent to which susceptibility is phylogenetically conserved among hosts is poorly understood and has rarely been appropriately tested. We screened for haemosporidian parasites in 3983 birds representing 40 families and 523 species, spanning ~4500 meters elevation in the tropical Andes. To quantify the influence of host phylogeny on infection status, we applied Bayesian phylogenetic multilevel models that included a suite of environmental, spatial, temporal, life history, and ecological predictors. We found evidence of deeply-conserved susceptibility across the avian tree; host phylogeny explained substantial variation in infection rate, and results were robust to phylogenetic uncertainty. Our study suggests that susceptibility is governed, in part, by conserved, latent aspects of anti-parasite defense. This demonstrates the importance of deep phylogeny for understanding the outcomes of present-day ecological interactions.\n\nStatement of authorshipLNB, SMM, NM, and CCW designed the study; SMM, SCG, HLL, HS, TV, JDW, and CCW collected the data; LNB and NM analyzed the data; LNB, NM, and CCW wrote the paper with input from all authors.\n\nData accessibility statementSpecimen information is available from the Arctos database (arctosdb.org) and in supplementary tables (Appendix S1). Files used for analysis will be archived in Dryad. DOI: XXX.

evolutionary biology↗

bioRxiv2018

Ecology, Not Distance, Explains Community Composition in Parasites of Sky-Island Audubon’s Warblers

O_LIHaemosporidian parasites of birds are ubiquitous in terrestrial ecosystems, but their coevolutionary dynamics remain poorly understood. If species turnover in parasites occurs at a finer scale than species turnover in hosts, widespread hosts would encounter diverse parasites and potentially diversify as a result. Previous studies have shown that some wide-ranging hosts encounter varied haemosporidian communities throughout their range, and vice-versa. However, it remains difficult to test spatial patterns of diversity in this complex multi-host multi-parasite system because it remains inadequately surveyed.\nC_LIO_LIWe sought to understand how and why a community of avian haemosporidian parasites varies in abundance and composition across an array of eight sky islands in southwestern North America. We tested whether bird community composition, aspects of the environment, or geographic distance explain parasite species turnover in a widespread, generalist host.\nC_LIO_LIWe sampled 178 Audubons Warblers (Setophaga auduboni) along elevational transects in eight mountain ranges and screened them for haemosporidian mtDNA. We tested predictors of infection using generalized linear models (GLMs) and we tested predictors of bird- and parasite-community dissimilarity using generalized dissimilarity modeling (GDM).\nC_LIO_LIPredictors of infection differed by genus: Parahaemoproteus was predicted by elevation and climate, Leucocytozoon varied idiosyncratically among mountain ranges, and Plasmodium was unpredictable, but rare. Parasite species turnover was nearly three-fold higher than bird species turnover and was predicted by elevation, climate, and bird community composition, but not by geographic distance.\nC_LIO_LIHaemosporidian communities vary strikingly at spatial scales of hundreds of kilometers, across which the bird community varies only subtly. The finer spatial scale of turnover among parasites species implies that their ranges tend to be smaller than those of their hosts. Avian host species should encounter different parasite species in different parts of their ranges, resulting in spatially varying selection on host immune systems. Furthermore, the fact that parasite turnover was predicted by bird turnover implies that different species within a host community affect each others parasites, potentially facilitating indirect antagonistic effects.\nC_LI

ecology↗

bioRxiv2017

Why are tropical mountain passes ‘low’ for some species? Genetic and stable-isotope tests for differentiation, migration, and expansion in elevational generalist songbirds

Most tropical bird species have narrow elevational ranges, likely reflecting climatic specialization. This is consistent with Janzens Rule, the tendency for mountain passes to be effectively higher in the tropics. Hence, those few tropical species that occur across broad elevational gradients raise questions. Are they being sundered by diversifying selection along the gradient? Does elevational movement cause them to resist diversification or specialization? Have they recently expanded, suggesting that elevational generalism is short-lived in geological time? Here we tested for differentiation, movement, and expansion in four elevational generalist songbird species on the Andean west slope. We used morphology and mtDNA to test for genetic differentiation between high- and low-elevation populations. Morphology differed for House Wren (Troglodytes aedon) and Hooded Siskin (Spinus magellanicus), but not for Cinereous Conebill (Conirostrum cinereum) and Rufous-collared Sparrow (Zonotrichia capensis), respectively. mtDNA was structured by elevation only in Z. capensis. To test for elevational movements, we measured hydrogen isotope ({delta}2H) values of metabolically inert feathers and metabolically active liver. {delta}2H data indicated elevational movements by two tree- and shrub-foraging species with moderate-to-high vagility (C. cinereum and S. magellanicus), and sedentary behavior by two terrestrial-foraging species with low-to-moderate vagility (T. aedon and Z. capensis). In S. magellanicus, elevational movements and lack of mtDNA structure contrast with striking morphological divergence, suggesting strong diversifying selection on body proportions across the [~]50 km gradient. All species except C. cinereum exhibited mtDNA-haplotype variation consistent with recent population expansion across the elevational gradient.In sum,three out of four elevational generalist species underwent genetic divergence despite gene flow, two of four make seasonal elevational movements, and three of four have recently expanded. In different ways, each species defies the tendency for tropical birds to have long-term stable distributions and sedentary habits. We conclude that tropical elevational generalism is rare due to evolutionary instability.

evolutionary biology↗