Abstract
Eurasian Nuthatches have experienced a northward range expansion in Britain. Younger, more isolated, populations have smaller song meme-pool size, diversity and individual repertoires.
Affichage des articles dont le libellé est Sitta europaea. Afficher tous les articles
Affichage des articles dont le libellé est Sitta europaea. Afficher tous les articles
MULTILOCUS COALESCENCE ANALYSES SUPPORT A mtDNA-BASED PHYLOGEOGRAPHIC HISTORY FOR A WIDESPREAD PALEARCTIC PASSERINE BIRD, SITTA EUROPAEA
Abstract
Our understanding of species phylogeography in much of the Palearctic is incomplete. In addition, many existing studies based solely on mitochondrial DNA (mtDNA) can provide a biased view of phylogeographic history because of the effects of lineage sorting, natural selection, or hybridization. We analyzed 13 introns to assess a mtDNA study of the Eurasian nuthatch (Sitta europaea) that suggested a seemingly contemporaneous origin of distinct taxa in the Caucasus, Europe, and Asia. Neutrality tests showed no evidence of selection on either the mtDNA or nuclear sequences. Most nuclear gene trees, except for Z-linked ones, did not recover the three lineages, which we attribute to recent splitting. Analyses of the 13 introns combined revealed the same three groups as did the mtDNA and suggested that nuthatches experienced a trichotomous (or two indistinguishable) split(s) 1–2 million years ago (Mya) and have remained isolated with trifling if not zero gene flow since then, and the Asian group increased in population size. This result demonstrates the usefulness of mtDNA in discovering phylogeographic patterns. The use of multiple nuclear loci facilitated detection of an introgressed individual and improved estimates of process parameters such as divergence time and population expansion. We recommend that phylogeographic studies should be based on both mtDNA and nuclear genes.
Keywords
Coalescence;divergence time;intron;mtDNA;phylogeography;selection
Year-round territorial aggression is independent of plasma DHEA in the European nuthatch Sittaeuropaea
Abstract
Plasma testosterone can play an important role in promoting aggressive behaviors relating to territory defense in breeding male birds. Some birds defend territories also during the non-breeding phase, when testosterone circulates at basal levels. In such species, plasma levels of the pro-hormone dehydroepiandrosterone (DHEA) may support non-breeding territoriality by acting as a local substrate for sex steroids. To test this possible role of plasma DHEA, we examined the seasonal DHEA profile of male (and female) European nuthatches Sitta europaea: a male and female nuthatch pair will defend an all-purpose territory throughout the year. We hypothesized that plasma DHEA would be detectable in wintering nuthatches with a territory. However, only ca. half of the territorial wintering males (and females) displayed detectable DHEA levels, suggesting that plasma DHEA is not a major sex steroid precursor during non-breeding. Further, among hatching-year birds, plasma DHEA was significantly lower in territorial birds than in “floaters”, i.e., subordinate birds without a territory. To experimentally examine the role of DHEA in non-breeding territoriality, we treated adult wintering males with DHEA and measured effects on aggressive responses to conspecific challenge. DHEA treatment elevated plasma levels of DHEA (and testosterone), but did not enhance territorial behaviors or their persistence. Taken together, our data suggest that DHEA (and, indeed, sex steroids per se) do not regulate non-breeding territoriality in the nuthatch. Given that territorial aggression in nuthatches is expressed year-round, a hormone for its activation may be redundant.
Highlights
► We examine the seasonal DHEA profile in a year-round territorial songbird. ► We test effects of DHEA treatment on non-breeding territoriality in autumn. ► Plasma DHEA shows no seasonal variation and is often undetectable. ► DHEA treatment does not enhance non-breeding aggression or its persistence. ► We report that DHEA does not relate to non-breeding territoriality in this species.
Keywords
Nuthatch; Seasonal DHEA profile; Implant; Territorial aggression; Testosterone; Non-breeding; Wintering
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