Species-Area Relationships Are Controlled by Species Traits

The species-area relationship (SAR) is one of the most thoroughly investigated empirical relationships in ecology. Two theories have been proposed to explain SARs: classical island biogeography theory and niche theory. Classical island biogeography theory considers the processes of persistence, extinction, and colonization, whereas niche theory focuses on species requirements, such as habitat and resource use. Recent studies have called for the unification of these two theories to better explain the underlying mechanisms that generates SARs. In this context, species traits that can be related to each theory seem promising. Here we analyzed the SARs of butterfly and moth assemblages on islands differing in size and isolation. We tested whether species traits modify the SAR and the response to isolation. In addition to the expected overall effects on the area, traits related to each of the two theories increased the model fit, from 69% up to 90%. Steeper slopes have been shown to have a particularly higher sensitivity to area, which was indicated by species with restricted range (slope  = 0.82), narrow dietary niche (slope  = 0.59), low abundance (slope  = 0.52), and low reproductive potential (slope  = 0.51). We concluded that considering species traits by analyzing SARs yields considerable potential for unifying island biogeography theory and niche theory, and that the systematic and predictable effects observed when considering traits can help to guide conservation and management actions

Effects of a fast-burning spring fire on the ground-dwelling spider assemblages (Arachnida: Araneae) in a central South African grassland habitat

Fire is widely used as a management strategy in grasslands to maintain vegetation structure and improve grazing quality for large herbivores. The impacts of burning on invertebrates in South Africa remain poorly understood. A study was initiated in spring 2005 to determine the impact of a fast hot burn on ground-dwelling spider assemblages in a grassland habitat in the central Free State. Pitfall traps were set out at six sites in the reserve, with three sites each in the burnt and unburnt areas, to sample spiders over a 12-month period. A total of 5 253 spiders were collected, representing 33 families and 120 species. Spider abundance was significantly lower in the burnt (n = 1 956) than unburnt sites (n = 3 297), and burnt sites had, on average, considerably fewer species than unburnt sites. The dominant families in the burnt sites were Lycosidae (29.5%), Gnaphosidae (16.9%), Ammoxenidae (9.6%) and Zodariidae (5.7%), whereas Ammoxenidae (22.7%), Lycosidae (20.6%), Gnaphosidae (15.3%) and Amaurobiidae (10.2%) dominated the unburnt sites. Of the nine most abundant families collected, only Caponiidae were more abundant in the burnt than unburnt sites. Our data suggest that fast-burning hot spring fires cause a considerable initial post-fire decline in spider abundance, and have a negative influence on the abundance as well as the resistance of assemblages to disturbances other than fire (e.g. rain). However, most of the dominant families had abundances comparable to unburnt areas within a year post-burn.http://www.tandfonline.com/loi/tafz202016-12-31hb201

Oocyte-specific inactivation of Omcg1 leads to DNA damage and c-Abl/TAp63-dependent oocyte death associated with dramatic remodeling of ovarian somatic cells

International audienceAberrant loss of oocytes following cancer treatments or genetic mutations leads to premature ovarian insufficiency (POI) associated with endocrine-related disorders in 1% of women. Therefore, understanding the mechanisms governing oocyte death is crucial for the preservation of female fertility. Here, we report the striking reproductive features of a novel mouse model of POI obtained through oocyte-specific inactivation (ocKO) of Omcg1/Zfp830 encoding a nuclear zinc finger protein involved in pre-mRNA processing. Genetic ablation of OMCG1 in early growing oocytes leads to reduced transcription, accumulation of DNA double-strand breaks and subsequent c-Abl/TAp63-dependent oocyte death, thus uncovering the key role of OMCG1 for oocyte genomic integrity. All adult Omcg1(ocKO) females displayed complete elimination of early growing oocytes and sterility. Unexpectedly, mutant females exhibited a normal onset of puberty and sexual receptivity. Detailed studies of Omcg1(ocKO) ovaries revealed that the ovarian somatic compartment underwent a dramatic structural and functional remodeling. This allowed the cooperation between oocyte-depleted follicles and interstitial tissue to produce estradiol. Moreover, despite early folliculogenesis arrest, mutant mice exhibited sexual cyclicity as shown by cyclical changes in estrogen secretion, vaginal epithelium cytology and genital tract weight. Collectively, our findings demonstrate the key role of Omcg1 for oocyte survival and highlight the contribution of p63 pathway in damaged oocyte elimination in adulthood. Moreover, our findings challenge the prevailing view that sexual cyclicity is tightly dependent upon the pace of folliculogenesis and luteal differentiation