Evolution and diversity of two cisco forms in an outlet of glacial Lake Algonquin

Abstract

The diversity of Laurentian Great Lakes ciscoes (Coregonus artedi, sensu lato) arose via repeated local adaptive divergence including deepwater ciscoes that are now extirpated or threatened. The nigripinnis form, or Blackfin Cisco, is extirpated from the Great Lakes and remains only in Lake Nipigon. Putative nigripinnis populations were recently discovered in sympatry with artedi in a historical drainage system of glacial Lake Algonquin, the precursor of lakes Michigan and Huron. Given the apparent convergence on Great Lakes form, we labeled this form blackfin. Here, we test the hypothesis that nigripinnis may have colonized this area from the Great Lakes as a distinct lineage. It would then represent a relict occurrence of the historical diversity of Great Lakes ciscoes. Alternatively, blackfin could have evolved in situ in several lakes. We captured more than 600 individuals in the benthic or pelagic habitat in 14 lakes in or near Algonquin Provincial Park (Ontario, Canada). Fish were compared based on habitat, morphology, and genetic variation at 6,676 SNPs. Contrary to our expectations, both cisco and blackfin belonged to an Atlantic lineage that colonized the area from the east, not from the Great Lakes. Sympatric cisco and blackfin were closely related while fish from different lakes were genetically differentiated, strongly suggesting the repeated in situ origin of each form. Across lakes, there was a continuum of ecological, morphological, and genetic differentiation that could be associated with alternative resources and lake characteristics. This study uncovers a new component of cisco diversity in inland lakes of Canada that evolved independently from ciscoes of the Laurentian Great lakes. The diversity of cisco revealed in this study and across their Canadian range presents a challenge for designating conservation units at the intraspecific level within the framework of the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).

Limited genetic parallelism underlies recent, repeated incipient speciation in geographically proximate populations of an Arctic fish (Salvelinus alpinus)

“…We also confirm the presence of genetically distinct morphs in Ramah detected previously using microsatellites (Salisbury et al, 2018). Genetic structure was driven primarily by location followed by morph type, as observed in other salmonid species (e.g., Larson et al, 2019;Piette-Lauzière et al, 2019;Prince et al, 2017), suggesting the relative evolutionary independence of morph radiations (Elmer & Meyer, 2011).…”

Isotopic niche size of Coregonus artedi (sensu lato) Increases in the presence of Mysis diluviana, expanded habitat use and phenotypic diversity

“…Given the capacity of Mysis to act as a food web engineer (Vander Zanden et al, 1999), the resulting planktonic composition and size structure may provide an adaptive trophic landscape that persists through time (or minimizes variability) that in turn provides ecological opportunity for cisco. This may also define the replicated diversity noted for cisco across inland and large lake ecosystems with Mysis (Piette-Lauzière et al, 2019;Turgeon & Bernatchez, 2003;Turgeon et al, 1999Turgeon et al, , 2016, and not colonization via glacial lake flooding that has historically been invoked, including the assumption of shared phylogenetic history, to account for consistency in cisco diversity across landscapes (Clarke, 1973;Dymond & Pritchard, 1930;Etnier & Skelton, 2003;Smith & Todd, 2004).…”

“…Following Eshenroder et al (2016), the term "form" has been adopted here to describe cisco with distinct phenotypes arising from in situ ecological speciation within C. artedi (sensu lato) as the recognized ancestral form. Here we refer to the ancestral, small pelagic form as cisco and the larger Mysis predator that has evolved in several lakes as blackfin (Bell et al, 2019;Piette-Lauzière et al, 2019).…”

“…Determining the mechanism(s) governing trade-offs in diel movement and preferred resting depths for cisco in any lake food web are complex and establishing the relative importance of factors such as minimizing predation, maximizing growth potential, or optimizing oxythermal habitat selection all have different levels of support in different lake ecosystems (Ahrenstorff et al, 2013;Hrabik et al, 2006;Jensen et al, 2006). While advances are being made in understanding cisco diversity (e.g., Ahrenstorff et al, 2013;Piette-Lauzière et al, 2019;Turgeon et al, 1999Turgeon et al, , 2016, insight into how food web structure fundamentally drives cisco diversity remains an elusive topic.…”

“…We compare cisco in Mysis versus Chaoborus food webs using isotopic trophic niche (Jackson et al, 2011;Swanson et al, 2015) and pose several hypotheses. Because cisco also occupy different habitats and/or have different phenotypic forms in Algonquin Park lakes with Mysis (Bell et al, 2019;Piette-Lauzière et al, 2019), we hypothesize that cisco (sensu lato) in these lake food webs will show greater isotopic niche size corresponding to greater habitat and/or phenotypic diversity (Eshenroderet al, 1998;Eshenroder & Burnham-Curtis, 1999), relative to Chaoborus-based food webs. Finally, we expect to find differences in the trophic niches of sympatric forms or fish found in pelagic versus benthic habitats within Mysis lakes.…”