Abstract
Climate change will have profound and unanticipated effects on species distributions. The pace and nature of this change is largely unstudied, especially for the most diverse elements of terrestrial communities – the arthropods – here we have only limited knowledge concerning the taxonomy and the ecology of these groups. Because Arctic ecosystems have already experienced significant increases in temperature over the past half century, shifts in community structure may already be in progress. Here we utilise collections of a particularly hyperdiverse insect group – parasitoid wasps (Hymenoptera; Braconidae; Microgastrinae) – at Churchill, Manitoba, Canada in the early and mid-twentieth century to compare the composition of the contemporary community to that present 50–70 years ago. Morphological and DNA barcoding results revealed the presence of 79 species of microgastrine wasps in collections from Churchill, but we estimate that 20% of the local fauna awaits detection. Species composition and diversity between the two time periods differ significantly; species that were most common in historic collections were not found in contemporary collections and vice versa. Using barcodes we compared these collections to others from across North America; contemporary Churchill species are most affiliated with more south-western collections, while historic collections were more affiliated with eastern collections. The past five decades has clearly seen a dramatic change of species composition within the area studied coincident with rising temperature.
Highlights
Changing global climate will affect species distributions, community composition and ecosystem function and these impacts are expected to be first evident in high elevation and high latitude communities [1,2,3]
By incorporating DNA barcoding with traditional taxonomy, we found that the communities of parasitoids uncovered in the 20th and 21st centuries were markedly different and that the species currently found in Churchill have a greater affiliation to southern species than did the community in the historic collection
About 20% of the microgastrine wasp species are still unknown and the species accumulation curve is far from asymptotic (Figure 1b) it is starting to flatten after 500 specimens
Summary
Changing global climate will affect species distributions, community composition and ecosystem function and these impacts are expected to be first evident in high elevation and high latitude communities [1,2,3]. There will be secondary impacts of climate changes, such as the disrupted phenological relationships between interacting species [5], including the altered synchronization between parasitoids and their host species [1]. Species will be prone to such alterations as the growing season is so short [6]. Accentuating this fear is our understanding of the ‘unknown unknowns’ of parasitoid biology: most species are undescribed – and their interrelationships within an ecological community remain invisible to scientific enquiry [7]. It is evident that further studies involving additional areas and regions will be necessary to better understand the diversity of parasitoid wasps
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