Ancient islands and modern invasions: disparate phylogeographic histories among Hispaniola’s endemic birds

Abstract

With its large size, complex topography and high number of avian endemics, Hispaniola appears to be a likely candidate for the in situ speciation of its avifauna, despite the worldwide rarity of avian speciation within single islands. We used multilocus comparative phylogeography techniques to examine the pattern and history of divergence in 11 endemic birds representing potential within-island speciation events. Haplotype and allele networks from mitochondrial ND2 and nuclear intron loci reveal a consistent pattern: phylogeographic divergence within or between closely related species is correlated with the likely distribution of ancient sea barriers that once divided Hispaniola into several smaller paleo-islands. Coalescent and mitochondrial clock dating of divergences indicate species-specific response to different geological events over the wide span of the island's history. We found no evidence that ecological or topographical complexity generated diversity, either by creating open niches or by restricting long-term gene flow. Thus, no true within-island speciation appears to have occurred among the species sampled on Hispaniola. Divergence events predating the merging of Hispaniola's paleo-island blocks cannot be considered in situ divergence, and postmerging divergence in response to episodic island segmentation by marine flooding probably represents in situ vicariance or interarchipelago speciation by dispersal. Our work highlights the necessity of considering island geologic history while investigating the speciation-area relationship in birds and other taxa.

Multilocus phylogenetic analyses of Hispaniolan and Bahamian trunk anoles (distichus species group)

“…Our analyses also recover a well-supported clade that 992 includes all three North paleo-island endemics (A. d. ignigularis, A. lands. Instead, our results favor previously hypothesized roles for 1000 vicariance due to sea level changes (Gifford et al, 2004;Gifford, 1001 2008; Gifford and Larson, 2008) and/or ecological processes 1002 (Townsend et al, 2007;Glor and Warren, 2011;Sly et al, 2011Sly et al, ) 1003 in the formation and maintenance of these lineages. Our sampling 1004 in this study does not allow us to distinguish between vicariance 1005 and ecological processes but further analyses, including niche 1006 modeling and lanscape genetics, could be used to examine their 1007 relative contributions to divergence in the distichus complex.…”

“…We test whether this valley represents an impor-180 tant biogeographic barrier to members of the distichus species 181 group by asking if taxa endemic to the North and South paleo-is-182 lands form distinct biogeographic clades. Evidence from birds 183 and other reptiles species has suggested two alternative scenarios 184 regarding this biogeographic barrier: dispersal between paleo-is-185 lands prior to their merger (Townsend et al, 2007;Glor and 186 Warren, 2011;Sly et al, 2011), and vicariance due to either salt-187 water intrusion or insuitable xeric habitat after paleo-island mer-188 ger (Gifford et al, 2004;Gifford, 2008;Gifford and Larson, 2008). 189 We also ask whether divergences in the distichus species group 190 likely occurred before or after paleo-island merger using 191 Bayesian divergence time estimates.…”

Robust Estimates of Divergence Times and Selection with a Poisson Random Field Model: A Case Study of Comparative Phylogeographic Data

“…The older divergence times in dry habitat birds correspond to the pattern observed in the mammalian fossil record that drier habitat taxa were the first to disperse across the Isthmus of Panama (Webb and Rancy 1996), but the median divergence times among groups were not significantly different. This finding is consistent with the conclusions of several comparative phylogeographic studies that recovered multiple episodes of divergence across barriers within a single assemblage of birds (Barber and Klicka 2010;Lim et al 2011;Sly et al 2011). Also, the assignment of sister pairs into discrete climatic groups may have limited our ability to detect significant differences among groups.…”

“…The other approach relies on estimating phylogeographic parameters from phylogenetic trees and coalescent modeling and then assesses the level of congruence in parameters among codistributed species. Both of these methodological frameworks have been used to evaluate the historical assembly of bird faunas from a range of systems, including the Neotropics (Burney and Brumfield 2009;, the Afrotropics (Voelker et al 2013), Australia (Huang et al 2011;Dolman and Joseph 2012), montane forests in Mexico (Barber and Klicka 2010), the Malay Archipelago (Lim et al 2011), North American deserts (Zink et al 2001), and the Caribbean (Sly et al 2011). An overall goal of both analytical approaches is to evaluate whether patterns inferred from neutral genetic variation are consistent with the predictions of geological changes or climatic fluctuations.…”

Full Issue

“…Colonization of islands sometimes involves loss of the capability for further long-distance dispersal, when flight is not integral to foraging, social interaction, or predator avoidance (McNab 1994, McNab and Ellis 2006, Steadman 2006. Reduction, and even loss, of flight capacity can be an adaptive response to island life, and some speciation may occur with adaptation of flightlessness, as a result of altered selective environments (Milá et al 2010, Sly et al 2011, Alonso et al 2012, Runemark et al 2012.…”