Classical Species Distribution Models are primarily based on climate, land use and other abiotic variables. Despite recent studies showing that biotic information can play an important role in shaping the distribution of species even at large scales, results are not always consistent among studies and the underlying factors that influence the importance of this biotic information to the models, are unclear. To address this knowledge gap, we evaluated how different factors affect the importance of biotic interactions in shaping species distributions, using fine-scale data from plant-pollinator and parasitic interactions in the Netherlands. We found that the models of wild bees improved, when their biotic interaction was included, and the model performance improved the most for parasitic bees. Taxonomic level, resolution and distribution range of the interacting species and degree of specialization of the modelled species all affected the importance of the biotic interactions to the models.

Aim The unique aquatic Pontocaspian (PC) biota of the Black Sea Basin (BSB) is in decline. Lack of detailed knowledge on the status and trends of species, populations and communities hampers a thorough risk assessment and precludes effective conservation. This paper aims to review PC biodiversity trends using endemic molluscs as a model group. We aim to assess changes in PC habitats, community structure and species distribution over the past century and to identify direct anthropogenic threats. Location Black Sea Basin (Bulgaria, Romania, Moldova, Ukraine and Russia). Methods Presence/absence data of target mollusc species was assembled from literature, reports and personal observations. PC biodiversity trends in the NW BSB coastal regions were established by comparing 20th and 21st century occurrences. Direct drivers of habitat and biodiversity change were identified and documented. Results A very strong decline of PC species and communities during the past century is driven by a) damming of rivers, b) habitat modifications negatively affecting salinity gradients, c) pollution and eutrophication, d) invasive alien species and e) climate change. Four out of 10 studied regions, namely, the Danube Delta – Razim Lake system, Dniester Liman, Dnieper-South Bug Estuary and Taganrog Bay-Don Delta contain the entire spectrum of ecological conditions to support PC communities and still host threatened endemic PC mollusc species. Distribution data is incomplete, but the scale of deterioration of PC species and communities is evident from the assembled data, as are major direct threats. Main conclusions PC biodiversity in the BSB is profoundly affected by human activities. Standardised observation and collection data as well as precise definition of PC biota and habitats are necessary for targeted conservation actions. This study will help to set the research and policy agenda required to improve data collection to accommodate effective conservation of the unique PC biota.

White-tailed bumblebee species, Bombus cryptarum, B. lucorum, B. magnus and B. terrestris are known to be very similar in their morphological characters across the majority of their ranges. This hampers assessment of their status and trends because reliable identification is difficult. In this study, we use a combination of characters and methods to assess how ecologists and citizen scientists can reliably and quickly separate these four species occurring in the Netherlands. Bumblebees (queens, workers and males) were sampled from 10 locations across the Netherlands and specimens were identified based on COI sequence data. Next, the same specimens where scored for morphological traits. We show that a combination of easy to recognise characteristics can separate some specimens of the species depending on caste and sex. Bombus magnus males and queens and B. lucorum males were most reliably separated from the other species using morphological characters. Workers of all four species cannot be separated completely using morphological characters alone. This is the first time standard morphological characters and ecological data has been used to study the differences between the white-tailed bumblebees in the Netherlands. Based on our findings we need to conclude that the status of these bumblebee species in the Netherlands is uncertain due to possible misidentifications in the past and present. People who wish to work with these species should be careful in species identification based on morphology.