Methylation patterns at fledging predict delayed dispersal in a cooperatively breeding bird

Individuals may delay dispersing from their natal habitat, even after maturation to adulthood. Such delays can have broad consequences from determining population structure to allowing an individual to gain indirect fitness by helping parents rear future offspring. Dispersal in species that use delayed dispersal is largely thought to be opportunistic; however, how individuals, particularly inexperienced juveniles, assess their environments to determine the appropriate time to disperse is unknown. One relatively unexplored possibility is that dispersal decisions are the result of epigenetic mechanisms interacting between a genome and environment during development to generate variable dispersive phenotypes. Here, we tested this using epiRADseq to compare genome-wide levels of DNA methylation of blood in cooperatively breeding chestnut-crowned babblers (Pomatostomus ruficeps). We measured dispersive and philopatric individuals at hatching, before fledging, and at 1 year (following when first year dispersal decisions would be made). We found that individuals that dispersed in their first year had a reduced proportion of methylated loci than philopatric individuals before fledging, but not at hatching or as adults. Further, individuals that dispersed in the first year had a greater number of loci change methylation state (i.e. gain or lose) between hatching and fledging. The existence and timing of these changes indicate some influence of development on epigenetic changes that may influence dispersal behavior. However, further work needs to be done to address exactly how developmental environments may be associated with dispersal decisions and which loci in particular are manipulated to generate such changes.

Inter-sexual and inter-generation differences in dispersal of a bivoltine butterfly

In organisms with discrete generations such as most insects, life-history traits including dispersal abilities often vary between generations. In particular, density-dependent differences in dispersal of bi- and multivoltine species may be expected because subsequent generations are usually characterized by a drastic increase in individual abundance. We investigated the inter-sexual and inter-generation differences in dispersal of a bivoltine butterfly, Lycaena helle, testing the following hypotheses: (1) male emigration is higher in spring generation, as males are prone to leave their natal habitat patches when the density of mating partners is low; (2) female emigration is higher in summer generation, when it helps to reduce intraspecific competition between offspring. The outcome of our analyses of dispersal parameters showed that females of the summer generation emigrated from their natal patches considerably more often than those of the spring generation, whereas an opposite trend was detected in males. These findings offer a novel perspective for our understanding of the advantages of voltinism for metapopulation functioning. The spring generation dispersal mainly improves the random mating opportunities favoured by the increase in male emigration. In turn, the dispersal of females of the summer generation appears the key to long-term metapopulation persistence.

Barn Swallow (Hirundo rustica) fledglings use crop habitat more frequently in relation to its availability than pasture and other habitat types

Populations of birds that forage on aerial insects have been declining across North America for several decades, but the main causes of and reasons for geographical variation in these declines remains unclear. We examined the habitat use and survival of post-fledging Barn Swallows (Hirundo rustica) near Vancouver, British Columbia, Canada, using VHF radio telemetry. We predicted that fledgling Barn Swallows hatched in higher-quality natal habitat (pasture) would fledge at higher quality, stay closest to the nest, disproportionately use higher-quality habitat during the post-fledge stage, and have higher survival rates in the region. Contrary to our predictions, we found that natal habitat (crop, pasture, or non-agriculture) had no effect on fledgling quality or movement distance. Barn Swallow fledglings used crop habitat more frequently in relation to its availability than other habitat types, including pasture. Barn Swallows had low post-fledging survival rates (0.44; 95% CI: 0.35–0.57), which could negatively influence the population trend of the species in this region. While natal habitat had only minor effects, crop habitat appears to be important for fledgling Barn Swallows and, therefore, a decline in this habitat type could have further negative implications for an already declining species.

Urban coyotes are genetically distinct from coyotes in natural habitats

Urbanization is increasing throughout the world, transforming natural habitats. Coyotes (Canis latrans) are found in highly urban, suburban, rural and undeveloped mountainous habitats, making them an exemplary model organism to investigate the effects of urbanization on animals. We hypothesized that coyotes in natural habitats are more genetically related to distant coyotes in similar natural habitats and less related to coyotes in urban areas due to natal habitat-biased dispersal. We also hypothesized that increasing urbanization would result in decreased genetic diversity due to habitat fragmentation, dispersal barriers and genetic drift. We analyzed 10 microsatellite genetic markers from 125 individual coyotes sampled across a spectrum of highly urban to highly natural areas in southern California. Most coyotes clustered into four distinct genetic populations, whereas others appeared to have admixed ancestry. Three genetic populations were associated primarily with urban habitats in Los Angeles and Orange Counties. In contrast, the remaining population was associated with more naturally vegetated land near the surrounding mountains. Coyotes living in natural areas formed a genetically distinct cluster despite long geographic distances separating them. Genetic diversity was negatively associated with urban/suburban land cover and local road density, and positively associated with the relative amount of natural vegetation. These results indicate that genetic differentiation and loss of genetic diversity coincided with the extremely rapid expansion of Greater Los Angeles throughout the 1900s. Thus, urbanization reduces gene flow and erodes genetic diversity even in a habitat generalist thought to be minimally impacted by land development.

Recurrent seasonal occurrence of the Lineated Woodpecker (Dryocopus lineatus) in a riparian fragment of the Atlantic Forest, northeastern Brazil

Riparian forests play important roles as ecological corridors and refuge habitat for many bird populations in fragmented landscapes. This report describes the seasonal occurrence of the Lineated Woodpecker (Dryocopus lineatus) in a small riparian fragment of Atlantic Forest, northeastern Brazil. A female was recorded by its visual and acoustical signals from September to October 2014. Similar occurrences were observed in the same months over three consecutive years. Two major hypotheses regarding the woodpecker seasonal occurrence are discussed here: i) the use of the riparian fragment for breeding, evidenced by tree-cavity nests; and ii) fleeing of the bird from its natal habitat due to fire in adjacent sugarcane fields, which commonly are burned in these two months. Such recurrent events suggest that D. lineatus uses the riparian fragment as refuge habitat, highlighting the importance of these environments for bird populations that inhabit fragmented landscapes of the Brazilian Atlantic Forest.

Home ground advantage: Local Atlantic salmon have higher reproductive fitness than dispersers in the wild

A long-held, but poorly tested, assumption in natural populations is that individuals that disperse into new areas for reproduction are at a disadvantage compared to individuals that reproduce in their natal habitat, underpinning the eco-evolutionary processes of local adaptation and ecological speciation. Here, we capitalize on fine-scale population structure and natural dispersal events to compare the reproductive success of local and dispersing individuals captured on the same spawning ground in four consecutive parent-offspring cohorts of wild Atlantic salmon (Salmo salar). Parentage analysis conducted on adults and juvenile fish showed that local females and males had 9.6 and 2.9 times higher reproductive success than dispersers, respectively. Our results reveal how higher reproductive success in local spawners compared to dispersers may act in natural populations to drive population divergence and promote local adaptation over microgeographic spatial scales without clear morphological differences between populations.

Strontium isotopes reveal ephemeral streams used for spawning and rearing by an imperilled potamodromous cyprinid Clear Lake hitch Lavinia exilicauda chi

Identification of habitats responsible for the successful production and recruitment of rare migratory species is a challenge in conservation biology. Here, a tool was developed to assess life stage linkages for the threatened potamodromous cyprinid Clear Lake hitch Lavinia exilicauda chi. Clear Lake hitch undertake migrations from Clear Lake (Lake County, CA, USA) into ephemeral tributary streams for spawning. An aqueous isoscape of strontium isotopic ratios (87Sr/86Sr) was constructed for Clear Lake and its watershed to trace natal origins and migration histories of adult recruits. Aqueous 87Sr/86Sr differentiated Clear Lake from 8 of 10 key tributaries and clustered into 5 strontium isotope groups (SIGs) with 100% classification success. Otolith 87Sr/86Sr showed all five groups contributed variably to the population. The age at which juveniles migrated from natal streams to Clear Lake ranged from 11 to 152 days (mean±s.d., 43±34 days) and was positively associated with the permanency of natal habitat. This information can be used by resource managers to develop conservation actions for Clear Lake hitch. This study demonstrates the utility of strontium isotopes in otoliths as a tool to identify important freshwater habitats occupied over the lifespan of an individual that would otherwise be challenging or impossible to trace with other methods.A