Acta Zoologica Cracoviensia, 59(2) 2016
Issue:
VOL 59(2) 2016
DOI:
10.3409/azc.59_2.177
Keywords:
Allen’s rule, Jungle Crow Corvus macrorhynchos, latitudinal cline, skullmorphology, Sakhalin Island
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Male-biased latitudinal cline of Jungle Crows on Sakhalin Island
Abstract:
Sakhalin Island, one of the largest islands in the Russian Federation, is isolated from the Eurasia continent by the Tatarsky Strait and from Japan’s Hokkaido Island by La Pérouse Strait. The island stretches in a meridional direction roughly 950 km and has maximum and minimum widths of 160 km and 26 km respectively. The Jungle Crow (Corvus macrorhynchos) inhabits the entirety of Sakhalin Island. No geographic barrier exists that would prevent crows from migrating between the southern and northern portions of the island. The entire island is in the oceanic climate zone and has a temperature seasonality that shows a clear gradation in the meridional direction, becoming progressively larger from south to north. The island thus has potential utility for addressing latitudinal variation in the Jungle Crow’s morphology. The author collected the crows serially from the south end of Sakhalin Island to the north end during June-July of 2007 breeding season. Two methods – the phenetic and metric approaches – were applied in the current skull-morphology study. Three phenetic traits, metric ten traits and body mass demonstrated neither clines nor gaps in latitudinal distribution for both sexes, with the exception of all five metric traits from the bill block in the male sample set. The male-biased cline, decreasing reversely from south to north, coincided with temperature seasonality; the cline in male bill size was found to be in accordance with Allen’s rule.
