A hitchhikers guide to the Galápagos: co-phylogeography of Galápagos mockingbirds and their parasites

Abstract

BackgroundParasites are evolutionary hitchhikers whose phylogenies often track the evolutionary history of their hosts. Incongruence in the evolutionary history of closely associated lineages can be explained through a variety of possible events including host switching and host independent speciation. However, in recently diverged lineages stochastic population processes, such as retention of ancestral polymorphism or secondary contact, can also explain discordant genealogies, even in fully co-speciating taxa. The relatively simple biogeographic arrangement of the Galápagos archipelago, compared with mainland biomes, provides a framework to identify stochastic and evolutionary informative components of genealogic data in these recently diverged organisms.ResultsMitochondrial DNA sequences were obtained for four species of Galápagos mockingbirds and three sympatric species of ectoparasites - two louse and one mite species. These data were complemented with nuclear EF1α sequences in selected samples of parasites and with information from microsatellite loci in the mockingbirds. Mitochondrial sequence data revealed differences in population genetic diversity between all taxa and varying degrees of topological congruence between host and parasite lineages. A very low level of genetic variability and lack of congruence was found in one of the louse parasites, which was excluded from subsequent joint analysis of mitochondrial data. The reconciled multi-species tree obtained from the analysis is congruent with both the nuclear data and the geological history of the islands.ConclusionsThe gene genealogies of Galápagos mockingbirds and two of their ectoparasites show strong phylogeographic correlations, with instances of incongruence mostly explained by ancestral genetic polymorphism. A third parasite genealogy shows low levels of genetic diversity and little evidence of co-phylogeny with their hosts. These differences can mostly be explained by variation in life-history characteristics, primarily host specificity and dispersal capabilities. We show that pooling genetic data from organisms living in close ecological association reveals a more accurate phylogeographic history for these taxa. Our results have implications for the conservation and taxonomy of Galápagos mockingbirds and their parasites.

Animals as Habitats

“…Since 1999, there has been an explosion of studies examining host-mite co-phylogenetic patterns, likely aided both by improvements in molecular phylogenetic methods and statistical approaches to testing hypotheses of co-diversifi cation. In most cases, a rigorous phylogenetic analysis of the mites is compared to previously published phylogenites/taxonomies of the hosts, but sometimes the authors include their own phylogenetic analysis of the hosts (e.g., Morelli and Spicer 2007 ;Štefka et al 2011 ). These studies have been at both the macro-and microevolutionary scales (Table 9.5 ).…”

Birds are islands for parasites

“…Given the high prevalence of these traits, congruent evolutionary histories are common between birds and their chewing lice [10,11]. Thus, bird-louse interactions are attractive systems to test for patterns of allopatric co-divergence.…”

Novel Primers From Informative Nuclear Loci for Louse Molecular Phylogenetics (Insecta: Phthiraptera)

“…Despite their importance as a model organism in hostÐparasite studies, very few loci have been targeted for sequencing in parasitic lice. A large number of studies have been published on the molecular phylogenetics of parasitic lice (Hafner et al 1994;Page et al 1998Page et al , 2004Cruickshank et al 2001;Johnson et al 2001aJohnson et al ,b, 2002aJohnson et al ,b, 2003Johnson et al , 2007Weckstein 2004;Banks et al 2005;Light and Hafner 2008;Š tefka and Hypsa 2008;Bueter et al 2009;Light et al 2010;Š tefka et al 2011), but most of these studies have only used short fragments of the mitochondrial cytochrome oxidase subunit-1 (CO1) and nuclear elongation factor-1 alpha (EF-1␣) for phylogenetic analysis. The generally small amount of data in these studies makes resolving many of the branches in the phylogenetic tree difÞcult.…”