Canadian Journal of Zoology, Volume 101, Issue 10, Page 869-885, October 2023.
We studied calls of three sandpiper species to document species’ similarities and differences. We hypothesized that functionally different calls would differ in degree of divergence. We studied two nuptial calls (complex “Song” and rhythmically repeated aerial call, RRC) of males, and a general-purpose call (“alarm” trill, AT) given by parents of both sexes in the presence of humans and other potential predators, in great knot, Calidris tenuirostris (Horsfeld, 1821); surfbird, Calidris virgata (Gmelin, 1789); and red knot, Calidris canutus (Linnaeus, 1758). Calls diverged unevenly across species—RRCs and Song diverged the most and ATs the least. Vocalizations of great knot and surfbird were most similar to one another, in agreement with a recently proposed phylogeny. Despite species differences in single acoustic traits, calls were evolutionarily conservative at higher structural levels, such as rhythmic temporal delivery of RRCs and harmonic structure (e.g., the fundamental frequency was suppressed in some call types). Some acoustic qualities that differed across species were similar across call types within species (e.g., tonality in red knot calls). Trait similarity across different calls suggests that a species’ calls cannot evolve independently of one another: common mechanisms of vocal production across different calls may impede differentiation within a species’ repertoire.

Canadian Journal of Zoology, Volume 101, Issue 10, Page 824-847, October 2023.
Allometric analyses of sexually selected structures have revealed many patterns of evolutionary and behavioural significance, for example, in weapons, ornaments, and genitalia. We investigated allometry of the baculum (penis bone) relative to body size in post-growth adults of three large mustelids: wolverine (Gulo gulo (Linnaeus, 1758)), northern river otter (Lontra canadensis (Linnaeus, 1758)), and sea otter (Enhydra lutris (Linnaeus, 1758)). The baculum grew over a longer period than did body size. Correlations among bacular variables were positive in post-growth adults. No regression slopes expressed positive allometry (i.e., slope > 1 for linear variables). These trends point to the possibility that bacular size is adapted to the average size of the reproductive tract of sexually mature female northern river otters and possibly sea otters, and that pre-ejaculatory (“pre-copulatory”) selection is highest in those species. Bacular size varied more than skull or limb-bone size, and bacular shape also varied greatly. Species differed in size and complexity of the urethral groove and bacular apex, suggesting functional differences in intromission. Substantial variation in bacular shape resulted from healed fractures, especially in sea otter. Knowledge of copulatory behaviour, age of breeding, female reproductive anatomy, and genitalic interactions during intromission is needed for comprehensive understanding of bacular anatomy, allometry, and variation for these species.