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Because cities concentrate 50% of the world’s population, and are experiencing a re-emergence of urban agriculture, we investigated the influences of urban agriculture and surrounding natural areas on floral visitors (bees, wasps, butterflies and flies) and plant species in San Cristobal de Las Casas, Mexico. Throughout the frost, dry and rainy seasons of 2015, we sampled floral visitors in nine urban gardens and nine natural areas. We found 210 floral visitor species: 78% pollinators, 18% predators, and 4% florivores. Rarefaction curves showed that natural areas harbor significantly more floral visitor species (148) than home gardens (132). However, the differences in species composition between habitats and seasons highlight the need to view natural areas and home gardens as complementary habitats with which floral visitors interact in varying ways, during successive seasons, to meet different needs. Furthermore, mean species richness of floral visitors was influenced mainly by seasonality, and increased as seasons progressed from the dry, frost season to the rainy season. Nonetheless, some taxa were influenced by both season and habitat type. Floral visitor abundance was influenced by both habitat type and season, with home gardens showing higher abundance across seasons. Moreover, interaction networks for each season were more asymmetric in natural areas than in home gardens. Urban cover in the surrounding landscape influenced in a quadratic way the species number of floral visitors, but not their abundance. Thus, our results are evidence that natural areas surrounding cities and urban agriculture contribute to floral visitor communities and their networks.

Climate oscillations have left a significant impact on the patterns of genetic diversity observed in numerous taxa. In this study, we examine the effect of Quaternary climate instability on population genetic variability of a bumble bee pollinator species, Bombus huntii in western North America. Pleistocene and contemporary B. huntii habitat suitability (HS) was estimated with an environmental niche model (ENM) by associating 1,035 locality records with 10 bioclimatic variables. To estimate genetic variability, we genotyped 380 individuals from 33 localities at 13 microsatellite loci. Bayesian inference was used to examine population structure with and without a priori specification of geographic locality. We compared isolation by distance (IBD) and isolation by resistance (IBR) models to examine population differentiation within and among the Bayesian inferred genetic clusters. Furthermore, we tested for the effect of environmental niche stability (ENS) on population genetic diversity with linear regression. As predicted, high‐latitude B. huntii habitats exhibit low ENS when compared to low‐latitude habitats. Two major genetic clusters of B. huntii inhabit western North America: (a) a north genetic cluster predominantly distributed north of 28°N and (b) a south genetic cluster distributed south of 28°N. In the south genetic cluser, both IBD and IBR models are significant. However, in the north genetic cluster, IBD is significant but not IBR. Furthermore, the IBR models suggest that low‐latitude montane populations are surrounded by habitat with low HS, possibly limiting dispersal, and ultimately gene flow between populations. Finally, we detected high genetic diversity across populations in regions that have been climatically unstable since the last glacial maximum (LGM), and low genetic diversity across populations in regions that have been climatically stable since the LGM. Understanding how species have responded to climate change has the potential to inform management and conservation decisions of both ecological and economic concerns.

Mexico and Central America are among the most biodiverse regions on Earth, harboring many species with high levels of interpopulation morphological and genetic diversity. The mountainous topography of this region contains isolated sky island habitats that have the potential to promote speciation. This has been studied in vertebrates, yet few studies have examined the phylogeographic and genetic structure of insect species encompassing this region. Here we investigate geographic patterns of genetic and morphological divergence and speciation among widespread populations of the highly polymorphic bumble bee Bombus ephippiatus and its closest relative B. wilmattae. We used DNA sequences from a fragment of cytochrome oxidase I (COI), genotypes for twelve microsatellite markers, and morphometric data from wings to construct a well-supported inference of the divergences among these taxa. We have found complex patterns of genetic isolation and morphological divergence within B. ephippiatus across its geographic range and present evidence that B. ephippiatus comprises multiple independent evolutionary lineages. The pattern of their diversification corresponds to geographic and environmental isolating mechanisms, including the Mexican highlands, the lowlands of the Isthmus of Tehuantepec in southern Mexico, the Nicaraguan Depression, the patchily distributed volcanic ranges in Nuclear Central America and Pleistocene glacial cycles. These results have important implications for the development and distribution of B. ephippiatus as a commercial pollinator in Mexico and Central America.