Size differentiation in Finnish house sparrows follows Bergmann's rule with evidence of local adaptation

Abstract

Bergmann's rule predicts that individuals are larger in more poleward populations and that this size gradient has an adaptive basis. Hence, phenotypic divergence in size traits between populations (P ST ) is expected to exceed the level of divergence by drift alone (F ST ). We measured 16 skeletal traits, body mass and wing length in 409 male and 296 female house sparrows Passer domesticus sampled in 12 populations throughout Finland, where the species has its northernmost European distributional margin. Morphometric differentiation across populations (P ST ) was compared with differentiation in 13 microsatellites (F ST ). We find that twelve traits phenotypically diverged more than F ST in both sexes, and an additional two traits diverged in males. The phenotypic divergence exceeded F ST in several traits to such a degree that findings were robust also to strong between-population environmental effects. Divergence was particularly strong in dimensions of the bill, making it a strong candidate for the study of adaptive molecular genetic divergence. Divergent traits increased in size in more northern populations. We conclude that house sparrows show evidence of an adaptive latitudinal size gradient consistent with Bergmann's rule on the modest spatial scale of ca. 600 km.

Do British birds conform to Bergmann's and Allen's rules? An analysis of body size variation with latitude for four species

“…Thus, with the exception of Robin, the results are broadly in agreement with Bergmann's rule. For female House Sparrow this result is consistent with published trends for the USA and Finland but unfortunately body mass was not used in these studies to enable a specific comparison of variation with latitude to be made (Johnston & Selander 1971, Brommer et al 2014.…”

“…For example, the House Sparrow Passer domesticus is a species that fits Bergmann's rule in the USA (Johnston & Selander 1971) and Finland (Brommer et al 2014). The Robin Erithacus rubecula is a sedentary native species and in contrast to House Sparrow, is commonly considered to exhibit only limited sexual dimorphism (Jovani et al 2012).…”

Strong phenotypic divergence in spite of low genetic structure in the endemic Mangrove Warbler subspecies (Setophaga petechia xanthotera) of Costa Rica

“…Under controlled conditions, phenotypic differences should be entirely due to additive genetic effects, so c/h 2 = 1 and P ST is equivalent to Q ST , and analogous to Q ST for a given quantitative trait (Wright, 1950). In wild populations, h 2 and c are usually difficult to estimate (Brommer, 2011) and nonadditive genetic effects such as selection can strongly influence the estimation of P ST (Brommer, 2011;Brommer, Hanski, Kekkonen, & Väisänen, 2014;Leinonen, Cano, Mäkinen, & Merilä, 2006;Pujol, Wilson, Ross, & Pannell, 2008). Consequently, we used a sequence of 100 values of c/h 2 between zero and two (Brommer, 2011).…”

Strong signature of selection in seeder populations but not in resprouters of the fynbos heathErica coccinea(Ericaceae)

“…This was done separately in the seeder and resprouter groups of populations to detect differences in the P ST ÀF ST contrasts between regeneration forms. (1) that the proportion of total variance due to additive genetic effects across populations (c. scalar) equals the heritability of the trait (h 2 ) (Brommer, 2011;Brommer et al, 2014). Saether et al, 2007;Wojcieszek & Simmons, 2012), we used the 99% level to be more conservative, as P ST tends to overestimate Q ST (Brommer, 2011;Young, Evans & Simmons, 2011).…”

“…Although P ST ÀF ST comparisons are normally carried out using 95% confidence intervals (e.g. To do so, we used the approach of Brommer et al (2014) of calculating, for each trait from eqn. Confidence intervals were calculated by the BCa method and 5000 bootstrap iterations using the 'boot' package in R (Canty & Ripley, 2008).…”