Reproductive Traits of an Invasive Alien Population of Grey Squirrel (Sciurus carolinensis) in Central Italy.

Margherita Maranesi,Cecilia Dall’Aglio,Marica Stazi,Giulia Moretti,Deborah Cruciani,Massimo Zerani,Silvia Crotti,Antonello Bufalari,Francesca Bergamasco,Antonio Di Meo,Cristiano Boiti,Daniele Paoloni,Elisabetta Manuali,Francesca Mercati

doi:10.3390/ani10040738

Abstract

The reproductive cycle of an invasive alien Italian grey squirrel population was studied to understand its adaptation and limit its spread, in order to conserve the autochthonous red squirrel. Female and male genital traits were evaluated throughout the reproductive cycle, including the ovary, uterus, testicle, epididymis, seminiferous tubule morphometry, and germinative epithelium histology. Moreover, individual female fecundity was determined by counting uterine scars. Ovary width and uterus weight, length, and width reached their highest values in the luteal and pregnancy phases. On conducting a histological evaluation of the testicular germinal epithelium, four morphotypes related to the different reproductive phases of the male squirrels were identified: immature, pubertal, spermatogenesis, and regressive. Testicle and epididymis weights and seminiferous tubule diameters reached their largest values during spermatogenesis. Uterine scar analysis showed that 69% of the females had given birth to one or two litters, while 31% had no uterine scars. Litters were larger in the first breeding period than in the second; annual fecundity was 4.52 ± 1.88 uterine scars/female. Umbrian grey squirrels have adapted to their non-native range, showing two annual mating periods at times similar to those in their native range, and high reproductive success.

Highlights

Invasive alien species (IAS) are one of the major drivers of biodiversity loss [1]
One of the best-known examples of competitive exclusion of a native species by an alien species is the replacement of the Eurasian red squirrel (Sciurus vulgaris) by the Eastern grey squirrel (Sciurus carolinensis) in Great Britain, Ireland, and Italy [8,9,10]
No differences were evident in ovary weight and length among the different reproductive phases, while ovarian width was significantly greater during the luteal and pregnant stages than during the other stages of the annual female reproductive cycle (p < 0.01; Table 1)

Summary

Introduction

Invasive alien species (IAS) are one of the major drivers of biodiversity loss [1]. These IAS can reduce or promote the extinction of native populations worldwide through different ecological processes [2], including interspecific competition [3], predation [4], transmission of infectious diseases [5], passing on helminths causing parasitological illness [6], and changes in ecosystems [7].One of the aims of the EU 2020 biodiversity strategy is to study IAS. Invasive alien species (IAS) are one of the major drivers of biodiversity loss [1]. These IAS can reduce or promote the extinction of native populations worldwide through different ecological processes [2], including interspecific competition [3], predation [4], transmission of infectious diseases [5], passing on helminths causing parasitological illness [6], and changes in ecosystems [7]. One of the best-known examples of competitive exclusion of a native species by an alien species is the replacement of the Eurasian red squirrel (Sciurus vulgaris) by the Eastern grey squirrel (Sciurus carolinensis) in Great Britain, Ireland, and Italy [8,9,10].

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Conclusion