Gene flow between two thick-billed grasswren subspecies with low dispersal creates a genomic pattern of isolation-by-distance

Context In the era of the Anthropocene, habitat loss and environmental change threaten the persistence of many species. Genotyping-By-Sequencing (GBS) is a useful molecular tool for understanding how patterns of gene flow are associated with contemporary habitat distributions that may be affected by environmental change. Two parapatric subspecies of the threatened thick-billed grasswren (TBGW; Amytornis modestus) more frequently occur in different plant communities. As such, a preference for plant community type could reduce subspecific introgression and increase genetic diversity at the parapatric boundary. Aims We aimed to measure gene flow within and among two TBGW subspecies and tested whether divergent genomic markers were associated with plant community type. Methods We sequenced 118 individuals from either of the two TBGW subspecies or in the region of parapatry and identified 7583 SNPs through ddRADseq. Key results We found evidence of asymmetric gene flow and a genomic pattern of isolation-by-distance. There were sixteen genomic outliers correlated with plant community type (regardless of location). Conclusions These findings show that plant community type does not prevent introgression in one subspecies (A. m. raglessi), but low dispersal and habitat heterogeneity could contribute to the maintenance of distinct subspecific morphotypes. Local adaptation in different plant community types could also provide a mechanism for future divergence. Implications We suggest subspecific introgression could increase genetic variation and the adaptive potential of the species, facilitating species persistence under conditions of climate change.

Karst sinkholes as foci of biodiversity in the Hoosier National Forest

Sinkholes are a well-known, but poorly studied, aspect of karst environments. In 2015, the Hoosier National Forest in southern Indiana, USA, commissioned a study of sinkhole habitats to assess their ecological role. The ecosystems of 26 sinkholes were evaluated to determine if sinkhole floor biological communities and species richness were a function of the surrounding plant community. Each sinkhole was sampled four times for five target groups of invertebrates at intervals of approximately three months, for a total of 104 visits. The sampling resulted in finding 140 taxa, including 31 land snails, 14 millipedes, 3 terrestrial isopods, 83 spiders and 9 pseudoscorpions. Of exceptional note were at least 12 new state records and a probable new species of pseudoscorpion. Several of these species appear to be endemic to sinkhole habitats. A link was confirmed between species richness and the surrounding plant community, specifically that the highest biodiversity was found in sinkholes surrounded by native deciduous forest, followed by native glades. Sinkholes in fields from which deciduous forest had been removed possessed markedly decreased species diversity, as did non-native plantings of pines. Sinkhole habitats had a significantly higher species richness than adjacent non-sinkhole control sites. Moreover, the arthropod communities that were found in each sinkhole within each plant community type were different from each other and the surrounding non-sinkhole areas. These data suggest that sinkholes are more than just depressions in epigean landscapes, but possess unique invertebrate communities linked to the surrounding plant community.

Understory Vegetation Change Following Woodland Reduction Varies by Plant Community Type and Seeding Status: A Region-Wide Assessment of Ecological Benefits and Risks

Woodland encroachment is a global issue linked to diminished ecosystem services, prompting the need for restoration efforts. However, restoration outcomes can be highly variable, making it difficult to interpret the ecological benefits and risks associated with woodland-reduction treatments within semiarid ecosystems. We addressed this uncertainty by assessing the magnitude and direction of vegetation change over a 15-year period at 129 sagebrush (Artemisia spp.) sites following pinyon (Pinus spp.) and juniper (Juniperus spp.) (P–J) reduction. Pretreatment vegetation indicated strong negative relationships between P–J cover and the abundance of understory plants (i.e., perennial grass and sagebrush cover) in most situations and all three components differed significantly among planned treatment types. Thus, to avoid confounding pretreatment vegetation and treatment type, we quantified overall treatment effects and tested whether distinct response patterns would be present among three dominant plant community types that vary in edaphic properties and occur within distinct temperature/precipitation regimes using meta-analysis (effect size = lnRR = ln[posttreatment cover/pretreatment cover]). We also quantified how restoration seedings contributed to overall changes in key understory vegetation components. Meta-analyses indicated that while P–J reduction caused significant positive overall effects on all shrub and herbaceous components (including invasive cheatgrass [Bromus tectorum] and exotic annual forbs), responses were contingent on treatment- and plant community-type combinations. Restoration seedings also had strong positive effects on understory vegetation by augmenting changes in perennial grass and perennial forb components, which similarly varied by plant community type. Collectively, our results identified specific situations where broad-scale efforts to reverse woodland encroachment substantially met short-term management goals of restoring valuable ecosystem services and where P–J reduction disposed certain plant community types to ecological risks, such as increasing the probability of native species displacement and stimulating an annual grass-fire cycle. Resource managers should carefully weigh these benefits and risks and incorporate additional, appropriate treatments and/or conservation measures for the unique preconditions of a given plant community in order to minimize exotic species responses and/or enhance desirable outcomes.

Globe flower Trollius europaeus L. in forest and forest edge communities of the northern part of Południowopodlaska Lowland

The distribution of Trollius europaeus in the northern part of the Południowopodlaska Lowland was described and a phytosociological study made of the localities where it was present between 2010 and 2012. The condition of all sites where T. europaeus was historically present was also verified. These field studies reveal that the number of sites of occurrence and the abundance of T. europaeus populations have rapidly diminished over recent years. Only 15 populations of the species in the vicinity of 7 sites were confirmed. Trollius europaeus is usually considered a species characteristic of moist meadows of ordo Molinietalia and in the plant community type, Polygono bistortae-Trollietum. In the northern part of the Południowopodlaska Lowland, no meadow sites containing Trollius europaeus still remain according to our survey. All the confirmed stands are situated in deciduous forests of class Querco-Fagetea (Tilio-Carpinetum and Potentillo albae-Quercetum) and moist forest edge communities of ordo Glechometalia. The disappearance of all meadow populations is mainly considered a result of intensification of the agricultural use of these habitats. We suggest that the category of threat to Trollius europaeus is increased on the regional list from VU to EN, and consolidated with further monitoring and active protection of stands where it is present