To date it is not well-understood how seasonality and human-induced habitat change may affect haemosporidian prevalence and parasitaemia in bird hosts in dryland habitats. We compared haemosporidian prevalence and parasitaemia between habitat types, including Yucca-dominated scrublands (closed habitat) and creosotebush scrublands (open habitat), and between seasons, including non-breeding (dry) and breeding (wet) in the Black-throated sparrow (Amphispiza bilineata) at semi-arid scrublands of Central Mexico. This bird species has different habitat preferences in comparison to other, previously studied species in the region; it shows higher abundances in open than in closed habitats and avoids urban areas. Overall haemosporidian prevalence was 22.1%. Prevalence and parasitaemia were higher for Haemoproteus sp. (Parahaemoproteus sp.) than Plasmodium. Variation in haemoparasitism was not associated with habitat type. This response differs from the previously recorded response in other bird species in the region for which haemoparasitism increases with increasing habitat degradation. Seasonality seems to be the most important driver of parasite infection for this sparrow as prevalence and parasitaemia were higher during the breeding than the non-breeding season. Two new lineages of Haemoproteus sp. that had not been reported before in any avian species were found through molecular diagnosis. A high diversity of haemosporidian lineages is shared among sites. More study is needed to understand the mechanisms that associate parasitaemia, prevalence, and specific environmental factors.

No abstract

The magnitude and distribution of genetic diversity through space and time can provide useful information relating to evolutionary potential and conservation status in threatened species. In assessing genetic diversity in species that are of conservation concern, several studies have focused on the use of Toll-like receptors (TLRs). TLRs are innate immune genes related to pathogen resistance, and polymorphisms may reflect not only levels of functional diversity, but may also be used to assess genetic diversity within and among populations. Here, we combined four potentially adaptive markers (TLRs) with one mitochondrial (COI) marker to evaluate genetic variation in the endangered Sierra Madre Sparrow (Xenospiza baileyi). This species offers an ideal model to investigate population and evolutionary genetic processes that may be occurring in a habitat restricted endangered species with disjunct populations (Mexico City and Durango), the census sizes of which differ by an order of magnitude. TLRs diversity in the Sierra Madre Sparrow was relatively high, which was not expected given its two small, geographically isolated populations. Genetic diversity was different (but not significantly so) between the two populations, with less diversity seen in the smaller Durango population. Population genetic structure between populations was due to isolation and different selective forces acting on different TLRs; population structure was also evident in COI. Reduction of genetic diversity in COI was observed over 20 years in the Durango population, a result likely caused by habitat loss, a factor which may be the main cause of diversity decline generally. Our results provide information related to the ways in which adaptive variation can be altered by demographic changes due to human-mediated habitat alterations. Furthermore, our findings may help to guide conservation schemes for both populations and their restricted habitat.