Mammary number and litter size of the fat dormouse on the Southern Caspian coast
2013
Naderi, Gholamreza | Kaboli, Mohammad | Karami, Mahmoud | Rezaei, Hamid R. | Lahoot, Masoud | Kamran, Mehdi | Koren, Toni | Kryštufek, Boris
Mammary number determines the nursing ability of a female and is an important factor in the evolution of litter size. We studied the variation in the number of nipples and the mean litter size in the fat dormouse Glis glis from northern Iran. Iranian dormice have on average more nipples (mean, 12.57±1.024) than their counterparts from northern Italy (11.25±0.85) and Slovenia (10.22±0.50). Different nipples are responsible for the variation in mammary numbers between populations: inguinal nipples vary in Slovenia, and abdominal nipples vary in Italy and Iran. We estimated the litter size in the Iranian fat dormouse to be equal to 7.85±0.89, which is evidently more than that reported in populations from northern Moravia (mean, 5.0) and Slovenia (mean, 5.8). The fact that fat dormice from Iran display higher mammary number and have more litters than their conspecifics from Europe conforms to the prediction of Gilbert’s empirical “one-half rule.” Owing to its highly specialized reproductive profile, the fat dormouse can adjust its fitness only by an increase of litter size, which in turn makes greater use of available nipples. We suggest that a greater nipple count may be selectively advantageous in the evolutionary perspective and that the Iranian population displays the most derived mammary number in the species.
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