Niche partitioning in a sympatric cryptic species complex

Abstract

Competition theory states that multiple species should not be able to occupy the same niche indefinitely. Morphologically, similar species are expected to be ecologically alike and exhibit little niche differentiation, which makes it difficult to explain the co‐occurrence of cryptic species. Here, we investigated interspecific niche differentiation within a complex of cryptic bumblebee species that co‐occur extensively in the United Kingdom. We compared the interspecific variation along different niche dimensions, to determine how they partition a niche to avoid competitive exclusion. We studied the species B. cryptarum, B. lucorum, and B. magnus at a single location in the northwest of Scotland throughout the flight season. Using mitochondrial DNA for species identification, we investigated differences in phenology, response to weather variables and forage use. We also estimated niche region and niche overlap between different castes of the three species. Our results show varying levels of niche partitioning between the bumblebee species along three niche dimensions. The species had contrasting phenologies: The phenology of B. magnus was delayed relative to the other two species, while B. cryptarum had a relatively extended phenology, with workers and males more common than B. lucorum early and late in the season. We found divergent thermal specialisation: In contrast to B. cryptarum and B. magnus, B. lucorum worker activity was skewed toward warmer, sunnier conditions, leading to interspecific temporal variation. Furthermore, the three species differentially exploited the available forage plants: In particular, unlike the other two species, B. magnus fed predominantly on species of heather. The results suggest that ecological divergence in different niche dimensions and spatio‐temporal heterogeneity in the environment may contribute to the persistence of cryptic species in sympatry. Furthermore, our study suggests that cryptic species provide distinct and unique ecosystem services, demonstrating that morphological similarity does not necessarily equate to ecological equivalence.

Cryptic species as a window into the paradigm shift of the species concept

“…Assuming that cryptic species significantly overlap in their ecological niche space, niche differentiation cannot explain their coexistence (Chesson, 2000). Several studies addressed this issue using various model organisms, including rotifers (Montero-Pau, Ramos-Rodr ıguez, Serra, & G omez, 2011;Ortells, Gomez, & Serra, 2003), nematodes (De Meester, Derycke, Bonte, & Moens, 2011;De Meester et al, 2016;Derycke et al, 2008), different amphipods (Cothran, Henderson, et al, 2013;Cothran, Noyes, & Relyea, 2015;Cothran, Stiff, Chapman, Wellborn, & Relyea, 2013;Dionne, Vergilino, Dufresne, Charles, & Nozais, 2011;Eisenring et al, 2016;Fi ser et al, 2015;Wellborn & Cothran, 2004), chironomids (Pfenninger & Nowak, 2008), bugs (Saleh, Laarif, Clouet, & Gauthier, 2012), bumble bees (Scriven, Whitehorn, Goulson, & Tinsley, 2016), fig wasps (Zhang, Lin, & Hanski, 2004) and bats (Ashrafi, Beck, Rutishauser, Arlettaz, & Bontadina, 2011;Nicholls & Racey, 2006;Rutishauser, Bontadina, Braunisch, Ashrafi, & Arlettaz, 2012). These studies unveiled emerging commonalities in co-occurrence patterns and unsolved issues with important implications for nature conservation.…”

Cuticular hydrocarbons as potential mediators of cryptic species divergence in a mutualistic ant association

“…Given that cryptic species are morphologically alike and often closely related, one would expect them to be ecologically very similar and to exhibit only slight niche differentiation (Violle, Nemergut, Pu, & Jiang, 2011). Already, very subtle ecological divergence in traits like thermal niche or food preferences, as well as spatio-temporal heterogeneity (e.g., different availability of resources), could allow such species to share the same habitat and avoid competitive exclusion (Gause, 1932;Hardin, 1960;Scriven, Whitehorn, Goulson, & Tinsley, 2016). In ants for example, cryptic species can occur sympatrically, if they inhabit distinct niches, for example, by specializing on different symbiotic fungi (Schultz et al, 2002).…”

Population genetics and sympatric divergence of the freshwater gudgeon, Gobiobotia filifer, in the Yangtze River inferred from mitochondrial DNA

“…The neotropical skipper butterfly Astraptes fulgerator is the best example (Hebert et al, ). Other animals, such as the bumble bee (Scriven, Whitehorn, Goulson, & Tinsley, ), mollusk (Sun et al, ), frog (Stuart, Inger, & Voris, ), and fish (Borsa, Hsiao, Carpenter, & Chen, ; Feulner, Kirschbaum, Schugardt, Ketmaier, & Tiedemann, ; Rosser, ), were also revealed to contain sympatric cryptic species as detected through mtDNA sequence analysis. The COI sequence is usually used as DNA barcoding for species identification with the criterion of 2% or 3% sequence divergence (e.g., Costa et al, ; Hebert et al, ; Loh, Bond, Ashton, Roberts, & Tibbetts, ; Shen, Guan, Wang, & Gan, ; Ward et al, ).…”

“…Other animals, such as the bumble bee (Scriven, Whitehorn, Goulson, & Tinsley, 2016), mollusk (Sun et al, 2016), frog (Stuart, Inger, & Voris, 2006), and fish (Borsa, Hsiao, Carpenter, & Chen, 2013;Feulner, Kirschbaum, Schugardt, Ketmaier, & Tiedemann, 2006;Rosser, 2015),…”