Effects of Patch Size and Type of Coffee Matrix on Ithomiine Butterfly Diversity and Dispersal in Cloud-Forest Fragments

Abstract: Determining the permeability of different types of landscape matrices to animal movement is essential for conserving populations in fragmented landscapes. We evaluated the effects of habitat patch size and matrix type on diversity, isolation, and dispersal of ithomiine butterflies in forest fragments surrounded by coffee agroecosystems in the Colombian Andes. Because ithomiines prefer a shaded understory, we expected the highest diversity and abundance in large fragments surrounded by shade coffee and the lowest in small fragments surrounded by sun coffee. We also thought shade coffee would favor butterfly dispersal and immigration into forest patches. We marked 9675 butterflies of 39 species in 12 forest patches over a year. Microclimate conditions were more similar to the forest interior in the shade‐coffee matrix than in the sun‐coffee matrix, but patch size and matrix type did not affect species richness and abundance in forest fragments. Furthermore, age structure and temporal recruitment patterns of the butterfly community were similar in all fragments, independent of patch size or matrix type. There were no differences in the numbers of butterflies flying in the matrices at two distances from the forest patch, but their behavior differed. Flight in the sun‐coffee matrix was rapid and directional, whereas butterflies in shade‐coffee matrix flew slowly. Seven out of 130 recaptured butterflies immigrated into patches in the shade‐coffee matrix, and one immigrated into a patch surrounded by sun coffee. Although the shade‐coffee matrix facilitated movement in the landscape, sun‐coffee matrix was not impermeable to butterflies. Ithomiines exhibited behavioral plasticity in habitat use and high mobility. These traits favor their persistence in heterogeneous landscapes, opening opportunities for their conservation. Understanding the dynamics and resource requirements of different organisms in rural landscapes is critical for identifying management options that address both animals’ and farmers’ needs.     

Urban Plants as Genetic Reservoirs or Threats to the Integrity of Bushland Plant Populations

Abstract:  Remnant plants in urban fringes and native plants in gardens have the potential to contribute to the conservation of threatened plants by increasing genetic diversity, effective size of populations, and levels of genetic connectedness. But they also pose a threat through the disruption of locally adapted gene pools. At Hyams Beach, New South Wales, Australia, four bushland stands of the rare shrub, Grevillea macleayana McGillivray, surround an urban area containing remnant and cultivated specimens of this species. Numbers of inflorescences per plant, fruits per plant, and visits by pollinators were similar for plants in urban gardens and bushland. Urban plants represented a substantial but complex genetic resource, displaying more genetic diversity than bushland plants judged by H_e , numbers of alleles per locus, and number of private alleles. Of 27 private alleles in urban plants, 17 occurred in a set of 19 exotic plants. Excluding the exotic plants, all five stands displayed a moderate differentiation ( F_ST = 0.14 ± 0.02), although the urban remnants clustered with two of the bushland stands. These patterns may be explained by high levels of selfing and inbreeding in this species and by long-distance dispersal (several seeds in the urban stand were fathered by plants in other stands). Genetic leakage (gene flow) from exotic plants to 321 seeds on surrounding remnant or bushland plants has not occurred. Our results demonstrate the conservation value of this group of urban plants, which are viable, productive, genetically diverse, and interconnected with bushland plants. Gene flow has apparently not yet led to genetic contamination of bushland populations, but high levels of inbreeding would make this a rare event and difficult to detect. Remnant plants in urban gardens could successfully contribute to recovery plans for endangered and vulnerable species.     

Negative Effects of Habitat Loss on Survival of Migrant Warblers in a Forest Mosaic

Abstract: Habitat loss and fragmentation in forested landscapes often negatively affect animal abundance; however, whether these factors also affect fitness is not well known. We hypothesized that observed decreases in bird occurrence and abundance in landscapes with harvested forests are associated with reduced apparent survival of adults. We defined apparent survival as an estimate of survival that accounts for an imperfect resighting probability, but not permanent emigration (i.e., dispersal). We examined the association between spatially extensive habitat loss and apparent survival of males of 2 Neotropical migrant species, Blackburnian Warbler (Dendroica fusca) and Black‐Throated Green Warbler (D. virens), over 7 years in the Greater Fundy Ecosystem, New Brunswick, Canada. We estimated apparent survival among and within breeding seasons. We quantified amount of habitat in the context of individual species. In this landscape, boundaries between land‐cover types are gradual rather than clearly identifiable and abrupt. Estimated apparent within‐season survival of both species decreased as a function of amount of habitat within a 2000‐m radius; survival was approximately 12 times (95% CI 3.43–14) greater in landscapes with 85% habitat than in landscapes with 10% habitat. Apparent annual survival also decreased as a function of amount of habitat within a 100‐m radius. Over the range of habitat amount, apparent annual survival decreased 15% (95% CI 7–29%) as the amount of habitat decreased. Our results suggest that reduced species occurrence in landscapes with low proportions of habitat is due partly to lower apparent survival at these sites. This mechanism operates both directly (i.e., via effects on mortality or dispersal during breeding) and possibly through indirect effects during the nonbreeding season. Habitat loss was associated not only with a lower number of individuals, but also with lower survival of those individuals.