Phylogenomics clarifies biogeographic and evolutionary history, and conservation status of West Indian tremblers and thrashers (Aves: Mimidae)

The West Indian avifauna has provided fundamental insights into island biogeography, taxon cycles, and the evolution of avian behavior. Our interpretations, however, rely on robust hypotheses of evolutionary relationships and consistent conclusions about taxonomic status in groups with many endemic island populations. Here we present a phylogenetic study of the West Indian thrashers, tremblers, and allies, an assemblage of at least 5 species found on 29 islands, which is considered the archipelago’s only avian radiation. We improve on previous phylogenetic studies of this group by using double-digest restriction site-associated DNA sequencing (ddRAD-seq) to broadly sample loci scattered across the nuclear genome. A variety of analyses, based on either nucleotide variation in 2,223 loci that were recovered in all samples or on 13,282 loci that were confidently scored as present or absent in all samples, converged on a single well-supported phylogenetic hypothesis. In contrast to previous studies, we found that the resident West Indian taxa form a monophyletic group, exclusive of the Neotropical–Nearctic migratory Gray Catbird Dumetella carolinensis, which breeds in North America. Earlier studies indicated that the Gray Catbird was nested within a clade of island resident species. Instead, our findings imply a single colonization of the West Indies without the need to invoke a subsequent ‘reverse colonization’ of the mainland by West Indian taxa. Furthermore, our study is the first to sample both endemic subspecies of the endangered White-breasted Thrasher Ramphocinclus brachyurus. We find that these subspecies have a long history of evolutionary independence with no evidence of gene flow, and are as genetically divergent from each other as other genera in the group. These findings support recognition of R. brachyurus (restricted to Martinique) and the Saint Lucia Thrasher R. sanctaeluciae as two distinct, single-island endemic species, and indicate the need to re-evaluate conservation plans for these taxa. Our results demonstrate the utility of phylogenomic datasets for generating robust systematic hypotheses.

Investigation of A Potential Relationship Between Wild Bird Populations and Human Lyme Disease Rate in Connecticut from 1991-2002

Lyme disease is the most common tick-borne disease in North America. Borrelia burgdorferi, is the pathogen, and the black-legged tick carries the bacteria and spreads it when feeding on the blood of animals and humans. At least 70 passerine species and one species of woodpecker in North American are parasitized by immature black-legged ticks. This hypothesis predicts that there would be a positive relationship between Lyme disease rates and bird numbers that infected with the pathogen, and there would be no relationship between Lyme disease rate and bird numbers that not known to be infected with the pathogen. I depended on the North American Breeding Bird Survey (BBS) to get bird species for 14 routes across Connecticut, and on the Connecticut DHS to get Lyme disease rates for the time period of the study (1991-2002). My bird data were: one group that included all 17 bird species that carry the pathogen, two species separately that are known to become infected by Lyme pathogen (American Robin and Gray Catbird), and a control species not known to carry the pathogen (American Redstart). I found significant positive relationships between bird numbers and human Lyme disease rate in two routes for the SCLP group, one route for American Robin, three routes for Gray Catbird, and two routes for American Redstart. Only Gray Catbird had a significant negative relationship with human Lyme disease rate in one route. Based on the positive relationships that appeared for American Redstart, the control species, and the few significant relationships for birds known to carry the pathogen, I reject the hypothesis that there is a strong relationship between numbers of birds that could be infected with B. burgdorferi and the rate of Lyme disease in people as measured by the methods used in this study.

Investigation of a Potential Relationship Between Wild Bird Populations and Human Lyme Disease Rate in Connecticut from 1991-2002

Lyme disease is the most common tick-borne disease in North America. Borrelia burgdorferi, is the pathogen, and the black-legged tick carries the bacteria and spreads it when feeding on the blood of animals and humans. At least 70 passerine species and one species of woodpecker in North American are parasitized by immature black-legged ticks. This hypothesis predicts that there would be a positive relationship between Lyme disease rates and bird numbers that infected with the pathogen, and there would be no relationship between Lyme disease rate and bird numbers that not known to be infected with the pathogen. The study depended on the North American Breeding Bird Survey (BBS) to get bird species for 14 routes across Connecticut, and on the Connecticut DHS to get Lyme disease rates for the time period of the study (1991-2002). The range of years was from 1991 to 2002 because of a change in how Lyme disease cases were reported starting in 2003. The bird data were: one group that included all 17 bird species that carry the pathogen, two species separately that are known to become infected by Lyme pathogen (American Robin and Gray Catbird), and a control species not known to carry the pathogen (American Redstart). The study found significant positive relationships between bird numbers and human Lyme disease rate in two routes for the SCLP group, one route for American Robin, three routes for Gray Catbird, and two routes for American Redstart. Only Gray Catbird had a significant negative relationship with human Lyme disease rate in one route. Based on the positive relationships that appeared for American Redstart, the control species, and the few significant relationships for birds known to carry the pathogen, the study rejected the hypothesis that there is a strong relationship between numbers of birds that could be infected with B. burgdorferi and the rate of Lyme disease in people as measured by the methods used in this study.