鱼类分批繁殖力和繁殖频率的研究进展

繁殖潜力是决定鱼类的繁殖补充及制定种群评估生物学假设的关键机制,由此分批繁殖力和繁殖频率对评估分批繁殖鱼类的繁殖潜力就十分必要.分批繁殖力和繁殖频率的研究均开始于20世纪80年代,在过去的30年中,评估分批繁殖力最为广泛使用的方法是水化卵法,而繁殖频率使用最多的方法是产后滤泡法.这两种方法虽然都存在一定的不足,但无可否认是现在最为实用和成熟的方法.     

Phenotypic divergence in reproductive traits of a moth population experiencing a phenological shift

Allochrony that is reproductive isolation by time may further lead to divergence of reproductive adaptive traits in response to different environmental pressures over time. A unique “summer” population of the pine processionary moth Thaumetopoea pityocampa, reproductively isolated from the typical winter populations by allochronic differentiation, is here analyzed. This allochronically shifted population reproduces in the spring and develops in the summer, whereas “winter” populations reproduce in the late summer and have winter larval development. Both summer and winter populations coexist in the same pine stands, yet they face different climatic pressures as their active stages are present in different seasons. The occurrence of significant differences between the reproductive traits of the summer population and the typical winter populations (either sympatric or allopatric) is thus hypothesized. Female fecundity, egg size, egg covering, and egg parasitism were analyzed showing that the egg load was lower and that egg size was higher in the summer population than in all the studied winter populations. The scales that cover the egg batches of T. pityocampa differed significantly between populations in shape and color, resulting in a looser and darker covering in the summer population. The single specialist egg parasitoid species of this moth was almost missing in the summer population, and the overall parasitism rates were lower than in the winter population. Results suggest the occurrence of phenotypic differentiation between the summer population and the typical T. pityocampa winter populations for the life‐history traits studied. This work provides an insight into how ecological divergence may follow the process of allochronic reproductive isolation.     

温度对麦蛾卵繁育的玉米螟赤眼蜂发育和生殖的影响

玉米螟赤眼蜂Trichogramma ostriniae Pang et Chen是玉米螟的重要卵寄生性天敌,控制适宜的温度有利于室内大规模繁育。本试验以麦蛾卵为寄主,研究了不同温度(18℃、20℃、23℃、25℃、28℃、30℃、33℃、36℃)对玉米螟赤眼蜂的寿命、生殖力、子代羽化率和发育历期的影响。结果表明,20℃-25℃条件下雌蜂寿命最长,达7.9-9.0 d。在18℃-30℃亲代生殖力和子代羽化率无显著差异,亲代产卵量为40.9-61.7粒;羽化率为74.31%-84.22%。玉米螟赤眼蜂从卵到羽化的发育历期随温度的升高而显著缩短,由18℃时的22.6 d缩短至33℃的7.0 d。36℃时,雌蜂的寿命仅为0.56 d,且不能进行正常的生殖活动。因此,室内用麦蛾卵大规模繁育玉米螟赤眼蜂,适宜的温度为28℃-30℃;仅保存蜂种时,可选用温度18℃-20℃。     

广东从化地区不同生境食蚊鱼种群的繁殖生物学特征

本文从繁殖群体的环境条件、形体特征、卵巢发育与繁殖力方面对广东从化地区溪流、池塘、农田3种不同生境的食蚊鱼(Gambusia affinis)种群展开比较研究。结果发现,无论流动水体溪流还是静水水体池塘和农田,食蚊鱼的繁殖期均在3~12月份,繁殖群体中雌鱼占比明显高于雄鱼(Chi-Square test,P0.01)。雌鱼周年平均体长及体重,池塘生境的显著大于农田和溪流生境。农田生境中雌鱼的个体怀卵量(24.1±12.1)粒,体重相对繁殖力(57.5±31.0)粒/g,二者均明显高于溪流生境[(16.6±11.6)粒,(40.8±15.5)粒/g]与池塘生境[(18.9±16.3)粒,(35.7±19.1)粒/g],但农田生境雌鱼成熟卵子的卵径显著小于溪流和池塘生境。结果表明,在环境稳定的池塘生境中,食蚊鱼的繁殖策略偏向k-对策特性;在人为干扰较大的农田生境中,食蚊鱼的繁殖策略偏向r-对策特性。不同类型生境中食蚊鱼的繁殖特性存在一定差异,主要与其栖息环境的稳定性和饵料生物的丰富度有关。     

韭菜迟眼蕈蚊雄虫日龄对其交配能力和雌虫生殖力的影响

为了提高韭菜迟眼蕈蚊性信息素监控水平,本文在25℃、RH70%±5%、光周期L∶D=14∶10的条件下研究韭菜迟眼蕈蚊不同日龄雄虫的交配能力及其对雌虫生殖力的影响。结果表明,未交配雄虫平均寿命4.5d,雌虫4.2d,雌雄成虫的平均寿命无显著差异。雄虫一生最多可交配13次,且随着雄虫日龄增加,雌虫交配成功率逐渐减少。随着雄虫交配经历的增加,雌虫交配的时间延长,最长达97min。雄虫的日龄并不影响与之交配雌虫的产卵量和卵孵化率,但是雄虫的交配经历与雌虫的产卵量和卵孵化率相关,尤其当雄虫交配经历超过8次时,与之交配的雌虫的产卵量和卵孵化率显著下降。研究阐明了韭菜迟眼蕈蚊的生殖行为特征,为其性信息素应用提供了参考。     

Geographic patterns of postzygotic isolation between two closely related widespread dung fly species (Sepsis cynipsea and Sepsis neocynipsea; Diptera: Sepsidae)

Identifying the contribution of pre‐ and postzygotic barriers to gene flow is a key goal of speciation research. The widespread dung fly species Sepsis cynipsea and Sepsis neocynipsea offer great potential for studying the speciation process over a range of opportunities for gene exchange within and across sister species (cross‐continental allopatry, continental parapatry and sympatry). We examined the role of postcopulatory isolating barriers by comparing female fecundity and egg‐to‐adult viability of F₁ and F₂ hybrids, as well as backcrosses of F₁ hybrids with the parental species, via replicated crosses of sym‐, para‐ and allopatric populations. Egg‐to‐adult viability was strongly but not totally suppressed in hybrids, and offspring production approached nil in the F₂ generation (hybrid breakdown), indicating yet unspecified intrinsic incompatibilities. Viable F₁ hybrid offspring showed almost absolute male (the heterogametic sex) sterility while females remained largely fertile, in accordance with Haldane's rule. Hybridization between the two species in European areas of sympatry (Swiss Alps) indicated only minor reinforcement based on fecundity traits. Crossing geographically isolated European and North American S. neocynipsea showed similar albeit weaker isolating barriers that are most easily explained by random genetic drift. We conclude that in this system with a biogeographic continuum of reproductive barriers, speciation is mediated primarily by genetic drift following dispersal of flies over a wide (allopatric) geographic range, with some role of natural or sexual selection in incidental or direct reinforcement of incompatibility mechanisms in areas of European sympatry. S(ubs)pecies status of continental S. neocynipsea appears warranted.     

Sterility of the coffee berry borer,Hypothenemus hampei (Coleoptera: Curculionidae), caused by the nematode Metaparasitylenchus hypothenemi (Tylenchidae: Allantonematidae)

Metaparasitylenchus hypothenemi is an endoparasitic nematode that causes partial or total sterility of coffee berry borer (Hypothenemus hampei) females, although the causes are unknown. Fecundity and the average size of the common and lateral oviduct, vitellarium, and germarium in the four ovarioles (I, II, III and IV) were compared between parasitised and non-parasitised insects to determine the causes of sterility. The nematode significantly lowers the number of oocytes and 86% of parasitised insects (24 out of 28 insects) were sterile, while fecundity in the remaining 13% was non-significantly different to that in non-parasitised insects. No significant differences were recorded in the size of the common oviduct, lateral oviduct, vitellarium, and germarium between parasitised and non-parasitised insects and the nematode does not cause any apparent damage on the surface of the ovary.     

A general framework for propagule dispersal in mangroves

Dispersal allows species to shift their distributions in response to changing climate conditions. As a result, dispersal is considered a key process contributing to a species' long‐term persistence. For many passive dispersers, fluid dynamics of wind and water fuel these movements and different species have developed remarkable adaptations for utilizing this energy to reach and colonize suitable habitats. The seafaring propagules (fruits and seeds) of mangroves represent an excellent example of such passive dispersal. Mangroves are halophytic woody plants that grow in the intertidal zones along tropical and subtropical shorelines and produce hydrochorous propagules with high dispersal potential. This results in exceptionally large coastal ranges across vast expanses of ocean and allows species to shift geographically and track the conditions to which they are adapted. This is particularly relevant given the challenges presented by rapid sea‐level rise, higher frequency and intensity of storms, and changes in regional precipitation and temperature regimes. However, despite its importance, the underlying drivers of mangrove dispersal have typically been studied in isolation, and a conceptual synthesis of mangrove oceanic dispersal across spatial scales is lacking. Here, we review current knowledge on mangrove propagule dispersal across the various stages of the dispersal process. Using a general framework, we outline the mechanisms and ecological processes that are known to modulate the spatial patterns of mangrove dispersal. We show that important dispersal factors remain understudied and that adequate empirical data on the determinants of dispersal are missing for most mangrove species. This review particularly aims to provide a baseline for developing future research agendas and field campaigns, filling current knowledge gaps and increasing our understanding of the processes that shape global mangrove distributions.     

Direct and indirect genetic effects on reproductive investment in a grasshopper

A fundamental part of the quantitative genetic theory deals with the partitioning of the phenotypic variance into additive genetic and environmental components. During interaction with conspecifics, the interaction partner becomes a part of the environment from the perspective of the focal individual. If the interaction effects have a genetic basis, they are called indirect genetic effects (IGEs) and can evolve along with direct genetic effects. Sexual reproduction is a classic context where potential conflict between males and females can arise from trade‐offs between current and future investments. We studied five female fecundity traits, egg length and number, egg pod length and number and latency to first egg pod, and estimated the direct and IGEs using a half‐sib breeding design in the grasshopper Chorthippus biguttulus. We found that the male IGEs were an order of magnitude lower than the direct genetic effects and were not significantly different from zero. However, there was some indication that IGEs were larger shortly after mating, consistent with the idea that IGEs fade with time after interaction. Female direct heritabilities were moderate to low. Simulation shows that the variance component estimates can appear larger with less data, calling for care when interpreting variance components estimated with low power. Our results illustrate that the contribution of male IGEs is overall low on the phenotypic variance of female fecundity traits. Thus, even in the relevant context of sexual conflict, the influence of male IGEs on the evolutionary trajectory of female reproductive traits is likely to be small.