Adaptive Radiation & Functional Morphology:

A major focus of my evolutionary research is directed towards understanding potential functionality of phenotypic variability within and among populations.

A:  Early studies (1970-1974) examined the ecological genetics of intertidal snails (Littorina mariae) which included evidence for microspatial matching between shell colour and background, mimicry between snails and spirorbid tubeworms, and influences of crab predation on shell morphology (R1979, 1981, 1982, 1989).  One of the interesting observations  in this study was that the interpretation of gastropod shell color required attention to the spatial geometry of predator and prey.  The bright yellow coloration of the littorine snails on the brown seaweeds was exceptionally conspicuous when viewed from the human standpoint but was highly camouflaged when viewed from the hunting positions of the intertidal fish, Blennius pholis, which hunted from beneath the algal fronds. These data indicated that the extent of phenotypic discreteness of the different color morphs among populations was coupled to the extent of substrate heterogeneity and microsubstrate discreteness.

B: Studies of threespine stickleback (Gasterosteus aculeatus ) on coastal archipelago of British Columbia including Haida Gwaii (Queen Charlotte Islands) and the Estevan Group, initially undertaken with Dr. G. E. Moodie from 1967 to 1970,  resumed in 1975 and have continued to the present.  These investigations have examined the functional morphology of bony plates, spines and  nuptial colour variation among 160 allopatric lake populations of stickleback from the Islands with special attention directed towards long term studies at two sites with divergent stickleback populations, Drizzle Lake and Boulton Lake (publications).

C: I have focussed on identifying causes of mortality in stickleback within and among the populations in an effort to identify selective landscapes relevant to defense morphology. The longest series of observations took place at Drizzle Lake where I monitored predator diversity over 10 years which in combination with short duration observations from the 160 allopatric populations indicated a more diverse selective landscape than previously inferred. Total yearly stickleback mortality at Drizzle Lake was structured by 23 species of piscine, avian, mammalian and macroinvertebrate piscivores of which the Common Loon and the Cutthroat trout are the major consumers (see figure below).  Different foraging efficiencies during the search, pursuit and manipulation phases among the different predator species may be a major predictor of selective landscape (R1994).

D: A series of four papers (R 1983; R 1992b; R 1994; R 2000) have provided experimental and field evidence for the functional morphology of the spine–plate defense apparatus of Gasterosteus. These traits which exhibit major geographical variation have been the focus of evolutionary studies for over the last 50 years and continue to be extensively investigated in evolutionary studies (review in Bell and Foster, 1994. Evolution of the Threespine Stickleback. Oxford Press: Bell 2001, Genetica 112:445-461), and most recently for the genetic basis of pelvic variation in vertebrates (Peichel et al. 2001. Nature 414:901-905).

E: Data obtained from long term field studies at Drizzle Lake and Boulton Lake, Haida Gwaii are consistent with multi-niche polymorphisms and adaptive variability within populations and provide evidence for cyclical seasonal selection on defense morphology (R 1995, R and Nosil 2002, 2004). This research suggests microspatial and microtemporal fine-tuning of morphology to a shifting selective landscape and provides a useful ecological framework for evaluating evolutionary rates based on the fossil record (Gingerich 2001, Genetica 112: 127-144) and are concordant with the investigations of  Galapagos finches (Grant and Grant 2002. Am. Sc. 90:130-139).

F: Based on a long standing interest (Moodie and Reimchen  1976, Systematic Zoology 25:49-61) in the evolutionary and ecological aspects of fluctuating and directional asymmetry in the defense apparatus of stickleback, my students and I have been able to provide useful field tests of hypotheses coupling asymmetry with fitness reduction using relative parasitism as a proxy for fitness  (R1997, Bergstrom and R 2000, 2002, 2003, 2005, R and Nosil 2001a, 2001b). Asymmetries are least frequent among lateral plates that buttress the dorsal and pelvic spines yet the asymmetries are unexpectedly common reaching 50% in some populations even with high levels of vertebrate predation.  We suspect that rather than relaxed selection, the high frequencies of asymmetries may comprise adaptive and functional responses to behavioral laterality in predators. Examination of bird-induced injuries on stickleback from Drizzle Lake shows evidence of laterality in capture . As an additional approach to these investigations of asymmetry, we are currently examining stable isotope signatures of stickleback from Boulton Lake and Drizzle Lake to test for possible niche differences of symmetric and asymmetric defense phenotypes (R et al. 2008; R&B 2009).   

The following figure shows the incidence of right side versus left side predator-induced pelvic fractures on stickleback
 from Drizzle Lake. Males have a greater incidence of left side fractures in littoral and limnetic habitats
 while females have a preponderance of right side fractures in limnetic but not in littoral habitats.




G: The perspectives emerging from the investigations of Gasterosteus from Haida Gwaii are that the population differentiation in defense morphology is largely driven by differences in predation regime, predator efficiencies and physical attributes of the habitat. Site-specific differences in the proportions of puncturing, compression and grappling piscivores alter the selection on pursuit versus manipulation adaptations of the stickleback . Water color, which varies from deeply stained to clear, influences the reaction distance between predator and prey which further shifts search, pursuit and manipulation failures among the predator species (see refs R 1992b, 1994, 2000).  These results appear to contrast with our recent investigations of insular Gasterosteus populations from the Banks- Estevan archipelago on the coastal mainland where water chemistry and lake morphometry are important predictors of trophic and defense morphology (Nosil and R 2005). The biophysicial attributes of the lakes are also associated with hydrodynamic aspects of body shape which is highly variable among the populations (Spoljaric and Reimchen  2007, 2008, 2011). The multiple replicated responses among the allopatric populations emphasize the deterministic processes in structuring population attributes.


                                                 General graphical model for the evolution of defense structures in Gasterosteus incorporating predator
                                         assemblage and predator-prey reaction distance derived from water spectra in stained and bluewater lakes  (Reimchen et al. 2013)





H:  The morphological and genomic differentiation of the Haida Gwaii stickleback, comprising over 100 endemic population, is ongoing.

Reimchen, Bergstrom & Nosil 2013 . Evolutionary Ecology Research 15: 241–269.

     "Natural selection and the adaptive radiation of  Haida Gwaii stickleback. "  

Deagle, BE., FC. Jones,  YF. Chan,  DB. Absher, DM. Kingsley, TE. Reimchen. 2012.    Proc. Roy. Soc.  279 : 1732 1277.
"Population genomics of parallel phenotypic evolution in stickleback across stream-lake ecological transitions."

Deagle, BE.,  FC. Jones, DM. Absher,  DM Kingsley & TE Reimchen. 2013.    Mol. Ecol. 22,:1917–1932.
                     " Phylogeography and adaptation genetics of stickleback  from the Haida Gwaii archipelago revealed using genome-wide
              single nucleotide polymorphism genotyping"

       Reimchen, TE, D. Steeves, & CA Bergstrom. 2016.  Evolutionary Ecology Research 17: 459-485.
"Sex matters for defense and trophic traits of threespine stickleback."

        Marques, DA , JS Taylor, FC Jone, F. Di Palma, D M. Kingsley & TE Reimchen. 2017.  PLOS Biology, in press.
                  " Convergent evolution of SWS2 opsin facilitates adaptive radiation of threespine stickleback into different light environments. "

I :This ecological and evolutionary research  have lead to several associated projects including parasitology of Gasterosteus (R1982, 1997, R & Nosil 2001b), dinoflagellate life history on endemic unarmoured Gasterosteus (R &  Buckland-Nicks 1990, Buckland-Nicks et al. 1990, 1995, 1996),  molecular phylogeny  of Haida Gwaii endemics (Byun et al. 1997, 1999, R & B 2005),  foraging and reproductive behaviour of Red-throated Loon (R & Douglas 1980, 1984, 1985, Douglas and R 1988a,b; see sonograms, audio clips, video clips, pdfs and links on home page for Sheila Douglas),  foraging behaviour of bears (R 1998a,b,  2000, Klinka and R 2002) and wolves (Darimont and Reimchen 2002; Darimont et al. 2003,  a functional analyses of  the 'vestigial' adipose fin in bony fishes (Reimchen and Temple 2004; Temple and Reimchen 2008; Buckland-Nicks et al. 2011),  biophysical inventories of aquatic habitats on Haida Gwaii (see Scientific Reports), nutrient cycling between marine and coastal oldgrowth forests (R 1994, 2000,  see Salmon Forest) and the ecological and evolutionary role of humans as superpredators (Darimont et al. 2015) .

  ......see full list of publications on Home Page 

Funding: Thanks to Natural Sciences and Engineering Research Council of Canada (NRC Operating Grant #2354 to T Reimchen)