Rapid morphological change in an insular population of feral sheep

Abstract

Artificially selected qualities can reduce fitness in a wild setting, thus feral domesticates should experience strong selective forces. Domestic sheep Ovis aries have frequently become feral on islands, which differ substantially from mainland environments. We examined changes in body mass and wool traits in feral sheep inhabiting Santa Cruz Island (SCI), California for Z90 years. To elucidate the influence of nutrition, we compared the mass of feral island sheep with that of island sheep raised in farm conditions. We found that feral sheep on SCI were smaller than purported founder breeds, and that most documented populations of insular feral sheep worldwide have converged to similar body sizes (within 6 kg). SCI rams attained greater mass in farm conditions but ewes did not, suggesting phenotypic plasticity in ram body mass. Ewes exhibited self-shedding of wool at a greater frequency than rams, and sex differences and shedding patterns were consistent with thermoregulation and the risk of fly strike disease as benefits of wool loss. Pigmentation rates did not increase, further supporting the influence of heat stress on wool traits. These changes occurred in o25 generations and may have had a genetic basis, representing a potential example of rapid evolution in insular feral sheep.

Population genomic, olfactory, dietary, and gut microbiota analyses demonstrate the unique evolutionary trajectory of feral pigs

“…Feralisation can be seen as a reversal of domestication, even if it does not result in the complete return to a wild “ancestral” form (Johnsson et al, 2016). This process has occurred independently on multiple occasions in populations of domesticated animals, such as chickens (Roberts, 1991), dogs (Zhang, Wang, et al, 2020), horses (Goodwin, 2007), pigs (Evin et al, 2015) and sheep (Van Vuren & Bakker, 2009). Thus, this phenomenon offers a unique opportunity to study how natural and sexual selection act on a domestic population whose survival is less immediately and less directly governed by humans (Der Sarkissian et al, 2015; Johnsson et al, 2016).…”

Evolutionary history of Scinax treefrogs on land‐bridge islands in south‐eastern Brazil

“…, 1991; Beerli et al. , 1996; Bittkau & Comes, 2005; Van Vuren & Bakker, 2010). Populations on land‐bridge islands are often the result of recent isolation from adjacent mainland populations, and therefore provide an ideal opportunity to examine the evolutionary processes that operate during initial species differentiation from the original source population (Velland, 2003; Velo‐Antón et al.…”

Genetic factors controlling wool shedding in a composite Easycare sheep flock

“…Historically, amongst farmed breeds in the UK, wool shedding has been observed and studied in the Wiltshire Horn, in studies comparing this breed to non‐shedding breeds such as Blackface and Tasmanian Merino sheep (Slee ; Slee & Carter ). The gene variants that lead to shedding are presumably the ancestral forms of the genes given that, in addition to being observed in the mouflon, this phenotype has been observed predominantly in feral sheep populations (Rudge ; Orwin & Whitaker ; Van Vuren & Bakker ), wild Soay sheep (Boyd et al . ; Ryder ; Doney et al .…”