Variation in fine‐scale genetic structure and local dispersal patterns between peripheral populations of a South American passerine bird

Abstract

The distribution of suitable habitat influences natal and breeding dispersal at small spatial scales, resulting in strong microgeographic genetic structure. Although environmental variation can promote interpopulation differences in dispersal behavior and local spatial patterns, the effects of distinct ecological conditions on within‐species variation in dispersal strategies and in fine‐scale genetic structure remain poorly understood. We studied local dispersal and fine‐scale genetic structure in the thorn‐tailed rayadito (Aphrastura spinicauda), a South American bird that breeds along a wide latitudinal gradient. We combine capture‐mark‐recapture data from eight breeding seasons and molecular genetics to compare two peripheral populations with contrasting environments in Chile: Navarino Island, a continuous and low density habitat, and Fray Jorge National Park, a fragmented, densely populated and more stressful environment. Natal dispersal showed no sex bias in Navarino but was female‐biased in the more dense population in Fray Jorge. In the latter, male movements were restricted, and some birds seemed to skip breeding in their first year, suggesting habitat saturation. Breeding dispersal was limited in both populations, with males being more philopatric than females. Spatial genetic autocorrelation analyzes using 13 polymorphic microsatellite loci confirmed the observed dispersal patterns: a fine‐scale genetic structure was only detectable for males in Fray Jorge for distances up to 450 m. Furthermore, two‐dimensional autocorrelation analyzes and estimates of genetic relatedness indicated that related males tended to be spatially clustered in this population. Our study shows evidence for context‐dependent variation in natal dispersal and corresponding local genetic structure in peripheral populations of this bird. It seems likely that the costs of dispersal are higher in the fragmented and higher density environment in Fray Jorge, particularly for males. The observed differences in microgeographic genetic structure for rayaditos might reflect the genetic consequences of population‐specific responses to contrasting environmental pressures near the range limits of its distribution.

Exploratory behavior, but not aggressiveness, is correlated with breeding dispersal propensity in the highly philopatric thorn‐tailed rayadito

“…Forest habitat in this area has been, and still is, subjected to a long and slow natural fragmentation process that is caused by a complex dynamic of tree regeneration (del‐Val et al , Kelt et al ). The total forest area in Fray Jorge extends to ~2.4 km 2 and it is comprised by several forest fragments (0.5–22.5 ha) that are distributed from north to south (Vergara and Marquet , Botero‐Delgadillo et al ). A total of 101–157 nestboxes were installed between 2006 and 2015 in forest patches, being regularly distributed (25–35 m) and geo‐referenced with 2 m measurement error.…”

“…We studied a population close to the northern limit of the species distribution, in Fray Jorge National Park, north‐central Chile, where a research project on its breeding biology has been carried out since 2007 using nestboxes. This is a relatively isolated population of rayaditos that breeds in a naturally fragmented forest surrounded by an extensive semiarid matrix (González and Wink , Yáñez , Quirici et al ), where local breeding dispersal is restricted and adult philopatry is common among female and male birds (Botero‐Delgadillo et al ). Because of the long‐term fragmentation process that has been taking place in this location (see below), dispersal phenotypes might have locally evolved as a response to an enduring heterogeneous landscape configuration, making this population of interest to investigate the correlation between dispersal and behavioral traits.…”

Does baseline corticosterone influence inter-annual apparent survival of the Thorn-tailed Rayadito?

“…So, the individual's environmental context and the phenotypic characteristics are likely to interact and affect fitness (e.g., [12,49]). In our study the populations differed not only in baseline Cort levels but in several environmental and historical characteristics, the high latitude population presents: (i) lower baseline Cort levels [34 35], (ii) inhabit a quasi-pristine environment, that have no restriction to dispersal [40] and (iii) present higher primary productivity and a more stable environment (lower Coefficient of variation: see Table 1, [34]). The low latitude population presents: (i) higher baseline Cort levels, (ii) inhabits a relict forest isolated from all other Rayadito populations [50] and (iii) the forest is maintained only because of a fog that originates from the nearby ocean [39].…”

“…As we had previously observed an absence of differences in baseline Cort levels between males and females [34] together with an absence of difference in survival probability between the sexes [40] we didn't separate capture history by sex (we didn't create two groups) (e.g., [32]). In order to maintain the same number of capture events (i.e., eight reproductive seasons), in the high latitude population we used encounter history form 2008 to 2015 and in the low latitude population from 2010 to 2017.…”

Long‐term within‐basin isolation patterns, different conservation units, and interspecific mitochondrial DNA introgression in an amphipod endemic to the ancient Lake Skadar system, Balkan Peninsula

“…The subsequent divergence events may reflect ongoing karstification and depletion of the local hydrological networks due to the general Pleistocene aridisation in southern Europe(Macklin, Lewin, & Woodward, 2012;Tzedakis, 2007).The fragmentation and isolation of habitats belonging to one water basin may lead to pronounced biodiversity, also at the genetic level(Botero-Delgadillo et al, 2017;Madeira et al, 2017). F I G U R E 4 Population connectivity illustrated by a matrix of pairwise F ST values for Homoeogammarus scutarensis.…”