Novel co‐occurrence of functionally redundant consumers induced by range expansion alters community structure

Abstract

Ongoing climate change is shifting the geographic distributions of some species, potentially imposing rapid changes in local community structure and ecosystem functioning. Besides changes in population‐level interspecific interactions, such range shifts may also cause changes in functional structure within the host assemblages, which can result in losses or gains in ecosystem functions. Because consumer‐resource dynamics are central to community regulation, functional reorganization driven by introduction of new consumer species can have large consequences on ecosystem functions. Here we experimentally examine the extent to which the recent poleward range expansion of the intertidal grazer limpet Scurria viridula along the coast of Chile has altered the role of the resident congeneric limpet S. zebrina, and whether the net collective impacts, and functional structure, of the entire herbivore guild have been modified by the introduction of this new member. We examined the functional role of Scurria species in controlling ephemeral algal cover, bare rock availability, and species richness and diversity, and compared the effects in the region of range overlap against their respective “native” abutted ranges. Experiments showed depression of per capita effects of the range‐expanded species within the region of overlap, suggesting environmental conditions negatively affect individual performance. In contrast, effects of S. zebrina were commonly invariant at its range edge. When comparing single species versus polycultures, effects on bare rock cover were altered by the presence of the other Scurria species, suggesting competition between Scurria species. Importantly, although the magnitude of S. viridula effects at the range overlap was reduced, its addition to the herbivore guild seems to complement and intensify the role of the guild in reducing green algal cover, species richness and increasing bare space provision. Our study thus highlights that range expansion of an herbivore can modify the functional guild structure in the recipient community. It also highlights the complexity of predicting how functional structure may change in the face of natural or human‐induced range expansions. There is a need for more field‐based examination of regional functional compensation, complementarity, or inhibition before we can construct a conceptual framework to anticipate the consequences of species range expansions.

Population genomic analyses reveal hybridization and marked differences in genetic structure of Scurria limpet sister species with parapatric distributions across the South Eastern Pacific

“…S viridula is distributed along the Peruvian province between 12 and 33°S, while S. zebrina is distributed along the transition zone between 31 and 42°S (Figure 1). Both species overlap on a narrow zone of approximately 250 km around the 31-33°S transition zone (Aguilera et al, 2020). Previous studies indicate that this overlap is recent and due to the southwards range expansion of S. viridula in the last 50 years (Rivadeneira & Fernández, this genetic break, with a significant proportion of them clustering in a single linkage group.…”

Pan-Arctic marine biodiversity and species co-occurrence patterns under recent climate

“…For instance, enhanced positive co-occurrences among fish taxa due to niche overlap increased prey-predator interactions and interspecific and asymmetric competition 50 . These also generate novel ecological interactions that could have implications for community structure and functioning 51,52 . It is also worth noting the significant drop in species co-occurrences (positive and negative) in the Davis-Baffin Bay over time, implying the potential www.nature.com/scientificreports/ loss of existing species association and trophic mismatches 53 .…”

Dynamic species interactions associated with the range-shifting marine gastropod Mexacanthina lugubris

“…In some cases, range-shifting species may compete with natives that are not able to undergo range shifts (or are unable to shift on pace with climate change), potentially leading to local extinctions. If endemic species become locally extinct, range-shifting species may be able to fill a comparable niche, but there are likely to be long-term effects, such as a shift in species assemblages and changes to population dynamics of interacting species (Flagor and Bourdeau 2018 ; Aguilera et al 2020 ). Because communities are unlikely to shift as a whole, climate-driven range shifts have the potential to alter community composition and ecosystem functioning.…”

“…Asynchronous and heterogeneous species responses can result in altered species interactions similar to those seen in non-native species introductions and invasions (reviewed in Wallingford et al 2020 ). However, few studies have assessed the effects of range-shifting species (e.g., species that are not directly introduced by anthropogenic activity) as they establish in new communities, despite the potential for significant impacts to communities and ecosystems (Sorte et al 2010 ; Pecl et al 2017 ; Aguilera et al 2020 ).…”