Contrasting effects of habitat discontinuity on three closely related fungivorous beetle species with diverging host-use patterns and dispersal ability

Coastal dunes as drivers of genetic differentiation in the honeypot ant Myrmecocystus baja (Formicidae: Formicinae)

Coastal dunes are unique habitats, threatened by human activities. In biogeographical terms, coastal dunes are habitat islands, being discrete and distinct patches of similar habitat among themselves, separated from each other by a different type of habitat. Furthermore, coastal dunes harbor endemic species, adapted to living solely in the habitats found on specific dune systems. For example, the honeypot ant Myrmecocystus baja is endemic and restricted to coastal dunes of Mexico's Baja California Pacific coast. This ecological and biogeographical scenario led to the questions whether their geographical isolation is reflected in their genetic diversity and structuring, and how their demographic history is related with the formation of the dune system habitats. To answer these questions, population genetic, isolation-with-migration, and phylogeographical analyses were carried out, based on mitochondrial and five nuclear intronic markers. Minimal gene flow was detected only between two of the dune systems sampled; otherwise, the M. baja populations were found to be isolated and genetically structured, and their divergence generally pre-dated the modern-day dune systems. It is therefore highly likely that these ants were already present in paleodunes and that each of the populations was established from founder populations as the dunes formed. These findings highlight the importance of coastal dunes for species such as the honeypot ant from Baja California, in promoting genetic differentiation.

Colonization routes uncovered in a widely introduced Mediterranean gecko, Tarentola mauritanica

In this study, we aimed to understand the contemporary and ancient colonization routes of the Moorish gecko, Tarentola mauritanica, using simple sequence repeats. By analyzing the genetic diversity of populations in different regions, we found that Morocco is the genetic diversity hotspot for the species, followed by the Iberian Peninsula. However, historical gene flow estimates identified the Iberian Peninsula, not Morocco, as the primary contributor of colonizing individuals, along with continental Italy to a lesser extent. Currently, mainland Italy is the main source of introduced individuals, likely due to the plant nursery trade. The study suggests that human-facilitated introductions from various geographical origins, with numerous regions colonized through continental Italy during two distinct periods, are responsible for the recurrent entry of individuals belonging to the European lineage of T. mauritanica into the Mediterranean and Macaronesia. These findings can inform better monitoring surveys and conservation programs by identifying putative current colonization routes of alien species.

Alternative measures of trait-niche relationships: A test on dispersal traits in saproxylic beetles

Functional trait approaches are common in ecology, but a lack of clear hypotheses on how traits relate to environmental gradients (i.e., trait-niche relationships) often makes uncovering mechanisms difficult. Furthermore, measures of community functional structure differ in their implications, yet inferences are seldom compared among metrics. Community-weighted mean trait values (CWMs), a common measure, are largely driven by the most common species and thus do not reflect community-wide trait-niche relationships per se. Alternatively, trait-niche relationships can be estimated across a larger group of species using hierarchical joint species distribution models (JSDMs), quantified by a parameter Γ. We investigated how inferences about trait-niche relationships are affected by the choice of metric. Using deadwood-dependent (saproxylic) beetles in fragmented Finnish forests, we followed a protocol for investigating trait-niche relationships by (1) identifying environmental filters (climate, forest age, and deadwood volume), (2) relating these to an ecological function (dispersal ability), and (3) identifying traits related to this function (wing morphology). We tested 18 hypothesized dispersal relationships using both CWM and Γ estimates across these environmental gradients. CWMs were more likely than Γ to show support for trait-niche relationships. Up to 13% of species' realized niches were explained by dispersal traits, but the directions of effects were consistent with fewer than 11%-39% of our 18 trait-niche hypotheses (depending on the metric used). This highlights the difficulty in connecting morphological traits and ecological functions in insects, despite the clear conceptual link between landscape connectivity and flight-related traits. Caution is thus warranted in hypothesis development, particularly where apparent trait-function links are less clear. Inferences differ when CWMs versus Γ estimates are used, necessitating the choice of a metric that reflects study questions. CWMs help explain the effects of environmental gradients on community trait composition, whereas the effects of traits on species' niches are better estimated using hierarchical JSDMs.

Omnivorous Notoxus trinotatus Pic (Coleoptera: Anthicidae) is a newly recognized vector of northern leaf blight in maize

The adaptations of omnivorous insects to food are manifested in a multifaceted manner, and the availability of food resources directly determines insect feeding tendencies, which contribute to a complex insect-food relationship and impact insect functionality in the environment. Stable isotope analysis was applied to test the feeding preference and further define the functional role of omnivorous beetles in cropland. Our results confirmed that as an omnivorous beetle, the fungivorous nature of Notoxus trinotatus accounted for a prominent proportion food selection at the adult stage, and more importantly, this dietary feature contributed to the dispersal of the northern corn leaf blight in maize (NLB) during the feeding trials. In addition to the preference for fungi, water supplementation was an essential element extending adult longevity, which directly prolonged the contact time of adults with pathogenic fungi in agricultural fields. Consistent with the herbivorous characteristics of beetles, before the emergence of NLB fungal pathogens, corn tissues served as the main food, which provided the beetles with more opportunities to transmit fungal pathogen propagules. We conclude that the role of N. trinotatus in carrying NLB pathogen is due to its feeding on this plant mycopathogen, and an increased abundance of beetles carrying the pathogen may increase the rate of NLB disease infestation. More focus should be concentrated on the functions of fungivorous beetles, not only as pathogen-transmitting pests, but also as an element among the balanced biotic factors in farmland.

Landscape genetics identifies barriers to Natterjack toad metapopulation dispersal

Habitat fragmentation and loss reduce population size and connectivity, which imperils populations. Functional connectivity is key for species persistence in human-modified landscapes. To inform species conservation management, we investigated spatial genetic structure, gene flow and inferred dispersal between twelve breeding sites of the Natterjack toad (Bufo calamita); regionally Red-Listed as Endangered in Ireland. Spatial genetic structure was determined using both Bayesian and non-Bayesian clustering analysis of 13 polymorphic microsatellite loci genotyping 247 individuals. We tested the influence of geographic distance, climate, habitat, geographical features, and anthropogenic pressure on pairwise genetic distances between breeding sites using Isolation-by-distance and Isolation-by-resistance based on least-cost path and circuit theory models of functional connectivity. There was clear spatial structuring with genetic distances increasing with geographic distance. Gene flow was best explained by Isolation-by-resistance models with coniferous forestry plantations, bog, marsh, moor and heath, scrub, anthropogenic presence (Human Influence Index) and rivers (riparian density) identified as habitats with high resistance to gene flow while metapopulation connectivity was enhanced by coastal habitats (beaches, sand dunes and salt marshes) and coastal grassland. Despite substantial declines in census numbers over the past 15 years and its regional status as Endangered, the Natterjack toad population in Ireland retains high genetic diversity. If declines continue, maintaining habitat connectivity to prevent genetic erosion by management of coastal grasslands, pond construction and assisted migration through translocation will be increasingly important.

Conservation genetics of relict tropical species of Magnolia (section Macrophylla)

Special conservation efforts should be made for relict species, as they usually have small population sizes and restricted distributions, placing them in critical extinction risk. To achieve conservation, information about genetic diversity distribution is needed. Here, using nine nuclear microsatellites, we analyzed 23 populations of five recently described species of Magnolia distributed in Mexico, which were previously assigned to Magnolia dealbata. We aimed to determine the level of genetic diversity and the distribution of genetic variation and proposed conservation measures. Compared to other endemic and relict species, we found a moderate level of genetic diversity in most populations; however, we identified two populations with no genetic variation. Additionally, we found evidence of positive values of inbreeding likely due to geitonogamy. We found a strong population structure, low effective population size, and no evidence of bottlenecks. Patterns of genetic differentiation did not support the morphological distinction of five species, so we hypothesized that the gene pools may instead represent well-differentiated populations of a single species. We argue that the pattern of genetic differentiation is explained by the natural fragmentation of the cloud forests after glaciation events, and the effects of genetic drift in small populations poorly connected by gene flow. Despite the moderate levels of genetic diversity, special attention is needed to guarantee conservation, with emphasis on the populations in the central region of the country as well as the valuable populations identified in the southwestern region.

Recent genetic connectivity and clinal variation in chimpanzees

Much like humans, chimpanzees occupy diverse habitats and exhibit extensive behavioural variability. However, chimpanzees are recognized as a discontinuous species, with four subspecies separated by historical geographic barriers. Nevertheless, their range-wide degree of genetic connectivity remains poorly resolved, mainly due to sampling limitations. By analyzing a geographically comprehensive sample set amplified at microsatellite markers that inform recent population history, we found that isolation by distance explains most of the range-wide genetic structure of chimpanzees. Furthermore, we did not identify spatial discontinuities corresponding with the recognized subspecies, suggesting that some of the subspecies-delineating geographic barriers were recently permeable to gene flow. Substantial range-wide genetic connectivity is consistent with the hypothesis that behavioural flexibility is a salient driver of chimpanzee responses to changing environmental conditions. Finally, our observation of strong local differentiation associated with recent anthropogenic pressures portends future loss of critical genetic diversity if habitat fragmentation and population isolation continue unabated.

Prediction of the Suitable Area of the Chinese White Pines (Pinus subsect. Strobus) under Climate Changes and Implications for Their Conservation

White pines (Pinus subsect. Strobus) play important roles in forest ecosystems in the Northern Hemisphere. Species of this group are narrowly distributed or endangered in China. In this study, we used a species distribution model (SDM) to project and predict the distribution patterns of the 12 species of Chinese white pine under a variety of paleoclimatic and future climate change scenarios based on 39 high-resolution environmental variables and 1459 distribution records. We also computed the centroid shift, range expansion/contraction, and suitability change of the current distribution area to assess the potential risk to each species in the future. The modeling results revealed that the suitable habitat of each species is consistent with but slightly larger than its actual distribution range and that temperature, precipitation, and UV radiation are important determining factors for the distribution of different white pine species. The results indicate that the Last Glacial Maximum (LGM) greatly affected the current distribution of the Chinese white pine species. Additionally, it was predicted that under the future climate change scenarios, there will be a reduction in the area of habitats suitable for P. armandii, P. morrisonicola, and P. mastersiana. Furthermore, some of the current distribution sites of P. armandii, P. kwangtungensis, P. mastersiana, P. morrisonicola, P. sibirica, and P. wallichiana were predicted to become more unsuitable under these scenarios. These results indicate that some Chinese white pine species, such as P. armandii, P. morrisonicola, and P. mastersiana, may have a very high risk of population shrinkage in the future. Overall, this study provided relevant data for the long-term conservation (both in situ and ex situ) and sustainable management of Chinese white pine species.