Reinforcement and learning

Evidence has been accumulating to support the process of reinforcement as a potential mechanism in speciation. In many species, mate choice decisions are influenced by cultural factors, including learned mating preferences (sexual imprinting) or learned mate attraction signals (e.g., bird song). It has been postulated that learning can have a strong impact on the likelihood of speciation and perhaps on the process of reinforcement, but no models have explicitly considered learning in a reinforcement context. We review the evidence that suggests that learning may be involved in speciation and reinforcement, and present a model of reinforcement via learned preferences. We show that not only can reinforcement occur when preferences are learned by imprinting, but that such preferences can maintain species differences easily in comparison with both autosomal and sex-linked genetically inherited preferences. We highlight the need for more explicit study of the connection between the behavioral process of learning and the evolutionary process of reinforcement in natural systems.     

The effect of prior adult experience on components of habitat preference in the apple maggot fly (Rhagoletis pomonella)

Summary Numerous authors have suggested that genetic subdivision within a population in a heterogeneous environment is more likely if individuals tend, through prior experience, to breed in the same habitat in which they developed. Under semi-field conditions we demonstrate that prior adult experience alters habitat preference in the apple maggot fly, Rhagoletis pomonella (Tephritidae), a frugivorous parasitic insect thought to have undergone sympatric divergence in host use in historical times. Females exposed to a particular host fruit species — apple (Malus pumila) or hawthorn (Crataegus mollis) — in a field cage oviposited at a higher rate in test fruit of that species than did inexperienced females or females exposed to the other species. Females exposed to a particular host fruit species also tended to remain longer in test trees harboring fruit of that species than did inexperienced females or females exposed to the other species. Prior adult experience thus alters two components of habitat preference in the apple maggot fly: oviposition preference and habitat fidelity. We discuss how these effects of experience on habitat preference should increase the likelihood that individuals mate assortatively and may further increase the likelihood that apple maggot populations become genetically subdivided.     

Home range size of willow tits: a response to winter habitat loss

We examined the behavioral response to habitat loss and fragmentation of willow tits (Parus montanus) in winter in a mosaic forest landscape in northern Finland. We studied habitat preference, flock size and home range size of 16 flocks, half of which had their territories in forests fragmented by forestry and half in continuous forest. We predicted that birds would respond to habitat loss by enlarging their home range and/or diminishing group size. In addition, to compensate for fragmentation effects, willow tits might be expected to include more optimal habitat into their territories. Flocks included on average 3.9 birds and occupied territories of 12.6 ha. Willow tits avoided open areas (clear cuts and young sapling stands) and preferred mature forests and older sapling stands or pine bogs equally. Birds responded to habitat loss by enlarging their home ranges but not by reducing the group size. Large territories included a smaller proportion of mature forests, but the proportion of sapling and pine bog habitat did not change. Birds on territories that included a large proportion of open habitat localized their activity on several distinct habitat patches that were distributed over a wide area. We conclude that willow tits adjust territory use to compensate for the inclusion of unsuitable habitat within home ranges, and older sapling areas and pine bogs serve as surrogates for mature forests. However, birds did not enlarge the proportion of forest habitat in their territories with increasing habitat loss. Thus, our data do not suggest a strong effect of fragmentation, but imply that forestry practices reduce suitable wintering habitat and carrying capacity in the area. Thus winter habitat loss may explain the observed population decline of willow tits in Finland during recent decades.     

Effect of turbidity on habitat preference of juvenile Atlantic cod, Gadus morhua

We examined the effects of turbidity on habitat preference of juvenile Atlantic cod in the laboratory, using a shuttle box where fish could select between two different habitats. In the first experiment, we compared three turbidity levels of kaolin (3, 8 and 21 beam attenuation m⁻¹). In the second experiment, we looked at the effect of turbidity media (kaolin versus algae), after controlling for spectral differences between turbidity media. Although cod preferred an intermediate turbidity of kaolin over low turbidity water, comparisons between low and high turbidity, and intermediate and high turbidity did not significantly influence habitat preference. Algae did not influence habitat preference by cod. Although other studies have found that turbidity affects both foraging and antipredator behaviour of juvenile cod, this study has shown that gradients in turbidity per se do not have a strong effect on their habitat preference.     

Biological structures and bottom type influence habitat choices made by Alaska flatfishes

Habitats of flatfishes are ordinarily characterized on the basis of depth, sediment type, and temperature. However, features of the benthic environment such as structures created by sessile organisms and different bedforms may also influence habitat suitability. In this investigation, we tested the hypothesis that habitat choices made by juveniles of two economically important flatfishes, Pacific halibut (Hippoglossus stenolepis Schmidt) and northern rock sole (Lepidopsetta polyxystra Orr and Matarese), are influenced by structures on the sea floor. In the laboratory, age-0 individuals of both species demonstrated high positive selectivity for habitats with structure (natural sponges, bryozoan mimics, bivalve shells, and sand waves) over smooth sand substratum. The degree of choice was influenced significantly by density of structures, particularly sponges. Small halibut (48-77 and 90-144 mm) were more selective than larger juveniles (270-337 mm), and in sponge habitat juvenile halibut were more selective than comparably sized rock sole. Preference for habitat with structure increased significantly with increasing light level, suggesting that choices were made partially on the basis of visual cues or as related to perceived threat. However, the preference for structured habitat was maintained in darkness. Beam trawl collections made in a flatfish nursery ground near Kodiak, Alaska, revealed that the abundances of age-0 Pacific halibut and rock sole were closely correlated with amounts of shell and echinoderm bycatch in the tows, corroborating the laboratory observations of affinity for habitat structure. Strong preferences for structured habitat in young halibut and rock sole indicate the importance of benthic structures that are frequently removed by fishing gear.     

Conserving a wetland butterfly: quantifying early lifestage survival through seasonal flooding, adult nectar, and habitat preference

Conservation of once thought extinct populations of Lycaena xanthoides in western Oregon will require specific information of how the butterfly interacts with its now rare wetland habitat. Three experiments were conducted to yield information directly applicable to wetland restoration work: (1) to quantify the survival of L. xanthoides eggs laid on inundated plants, (2) to quantify adult nectar preferences, (3) to investigate the role of adult resources and how butterflies assess habitat quality. Survival of eggs laid on inundated plants was nearly seven times lower than the survival of eggs laid on uninundated plants, indicating that eggs laid on plants that are seasonally flooded are a population sink. Adult L. xanthoides preferred an endemic native nectar plant, Grindelia integrifolia × nana, as an adult resource and used it approximately 88% of the time while other butterfly species preferred to nectar on the non-native Mentha pulegium. Adult L. xanthoides had a significantly greater short-term recapture rate in two restored study sites that had a high relative amount of Grindelia integrifolia × nana compared to a degraded site that lacked the preferred nectar source. Based on the results from the three small experiments, restoration of wetlands for L. xanthoides should concentrate plantings of host plant in non-flooded areas and propagate conspicuous patches of the preferred nectar plant.     

Deterioration of cichlid habitat by increased sedimentation in the rocky littoral zone of Lake Malawi

Lake Malawi has been affected by soil erosion across the catchment area. We experimentally investigated habitat preferences of cichlids in the rocky littoral zone to examine the influence of increased sedimentation on bottom-dwelling cichlids. Numbers of individuals and species, as well as the feeding rate of some of these cichlids, increased following the clearing of sediment. The results showed that these cichlids preferred sediment-free bottom and that the sedimentation causes deterioration of their habitats. Studies on the consequences of the habitat deterioration caused by increased sedimentation are needed in the management of these most diverse freshwater fish communities.     

Impact of habitat modification on the distribution and abundance of fruit flies (Diptera: Tephritidae) in Southeast Queensland

Loss of rainforest because of agricultural and urban development may impact the abundance and diversity of species that are rainforest natives. Tropical fruit flies are one group of such organisms indigenous to rainforests. In southeast Queensland, a region subject to rapid urbanization, we assessed the impact of habitat disturbance on the distribution and abundance of native fruit flies. Data on four species (Bactrocera tryoni, Bactrocera neohumeralis, Bactrocera chorista, and Dacus aequalis) were gathered and analyzed over 6 months in three habitat types: suburbia, open sclerophyll forest, and rainforest. We also analyzed the data at a combined "dacine fruit fly" level incorporating all fruit fly species trapped over the period of study (as might occur in a biodiversity assessment): these included the four species already named and Bactrocera melas, Bactrocera bryoniae, Bactrocera newmani, and Dacus absonifacies. Analysis at the species level showed that the polyphagous pest species responded differently to the monophagous species. Bactrocera tryoni, which has more exotic than native hosts, was positively affected by transformation of natural habitat into suburbia whereas B. neohumeralis, which has nearly identical numbers of native and exotic hosts, was found equally across habitat types. Bactrocera chorista and Dacus aequalis, each monophagous on a species-specific rainforest host plant, were most abundant in rainforest. The analysis based on the combined data suggests that replacing rainforest with suburbia has a neutral, or even positive, effect on the abundance of fruit flies as a whole. At the species level, however, it can be seen that this is an erroneous conclusion biased by the abundance of a single pest species. Our discussion raises the issue of analyses at supraspecific levels in biodiversity and impact assessment studies. Received: March 6, 2000 / Accepted: June 19, 2000     

Back-and-forth shifts in habitat selection by giant pandas over the past two decades in the Daxiangling Mountains,southwestern China

Habitat selection is a complex process, and animals may change their habitat selection over time. However, we have a poor understanding of temporal variation in habitat selection of endangered giant pandas (Ailuropoda melanoleuca), which has limited the development of conservation strategies for them. This study examined giant panda habitat selection in three stages of the past two decades (2001–2002, 2011–2012, and 2019–2020) in the Daxiangling Mountains, southwestern China. We applied the resource selection function to estimate the probability of species occurrence with five limiting habitat factors, i.e., elevation, slope, aspect, tree diameter at breast height, and bamboo cover. We found that giant pandas consistently selected for south- and west-facing slopes with mid-elevations and large trees in the three stages. However, there were shifts back-and-forth in the choice between higher and lower elevations and between higher and lower bamboo cover across the three stages. We suggest that the giant panda habitat selection had important consequences for gaining the high availability of palatable bamboo and good shelters. The back-and-forth shifts might be the result of changes in the type, spatial distribution, and intensity of human disturbance. Our study provides insights for improving our understanding and approaches for quantifying temporal variation in habitat selection in giant pandas and other species, suggesting that adaptive conservation and management in response to changing environments is needed.     

Speciation and legislation

Abstract

The chemical speciation of milks containing trace levels of aluminium defies experimental analysis because of the extremely low concentrations and labile equilibria present. Nevertheless, atomic absorption spectrophotometry data in combination with precisely determined formation constants have been used to construct speciation models simulated using the ECCLES computer program and the Cardiff thermodynamic database.

Formation constants for the Al³⁺-citrate, -succinate, -picolinate, and -malate systems are reported for 37°C and I = 150 mmol dm^?3. Total aluminium concentrations in a range of commercially available bovine milks are given.

In general, the major aluminium species present are charged citrate complexes which present little or no apparent threat to a healthy human as such complexes will not be absorbed through the intestinal walls. However, the importance of phosphate binding is revealed and further studies recommended.     

Distribution and habitat preferences of species within the genus Elaphoidella Chappuis, 1929 (Crustacea: Copepoda: Harpacticoida) in Slovenia

Twelve species of the harpacticoid genus Elaphoidella, most of them exclusively groundwater species, have been recorded in Slovenia (SE Europe). Their distribution and ecology are reviewed with the aim of evaluating distribution patterns, species preferences for groundwater habitats, ecological preferences and interactions with other copepod species at regional scale. Data on Elaphoidella species were obtained partly from the existing literature and partly from the author's (AB) own sampling campaigns carried out together with his co-workers. During the rich history of collecting copepods in Slovenia (from the 1920s to present), Elaphoidella species were recorded at 78 sampling sites altogether. The majority of collecting was conducted in the southern (Dinaric region) and north-western (Alpine region) Slovenia. The most intensively sampled habitats were porous aquifers of alluvial plains, springs in the karstic unsaturated zone and percolation water in caves. The highest species richness of Elaphoidella was recorded in the southern Slovenia, where 10 species were found. The strictly “Dinaric” species are E. charon, E. franci, E. karstica, E. stammeri, E. sp. 1 and E. sp. 2, while E. phreatica and E. bidens were found exclusively in the north-western Slovenia. From the latest data on the copepod distributions (2002–2004), where the environmental characteristics of sampling sites were also measured, the relationship between selected environmental characteristics of the habitats and the presence of Elaphoidella species was analysed. The distribution of Elaphoidella species in Slovenia was found to be related with the region, habitat type, altitude, conductivity and pH of the water.     

Species‐habitat associations change in a subtropical forest of China

Question: Do tree and shrub species in an evergreen broadleaf forest show similar habitat associations across different life stages? Location: A 24‐ha evergreen broadleaf forest plot in a heterogeneous landscape in Gutianshan National Nature Reserve, Zhejiang Province, Eastern China. Methods: Species having positive associations with four habitat types (low valley, low ridge, upper valley, and upper ridge) at three life stages (sapling, juvenile, and mature stages) were compared for 60 tree and shrub species using torus‐translation tests. Results: A total of 117 significant positive associations with the four habitats were observed at the three life stages (43, 41, and 33 at the sapling, juvenile, and mature stages, respectively). For the 52 species significantly associated with habitats, only 16 were associated with the same habitat across all three stages. The majority of associated species at the juvenile stage (34 out of 40) were associated with the same habitat at their sapling stage, whereas half of species at the mature stage had consistent associations with the same habitat at their sapling stage. More species were associated with the upper ridge at the sapling and juvenile stages compared to the mature stage. Conversely, more species were associated with the low valley at the mature stage compared to the sapling and juvenile stages. Conclusions: Our results indicate that species ecological habitat associations can differ between developmental stages beyond 1 cm DBH, as most species habitat preferences were consistent from the sapling stage to the juvenile stage but changed at the mature stage.     

Speciation and Bursts of Evolution

A longstanding debate in evolutionary biology concerns whether species diverge gradually through time or by rapid punctuational bursts at the time of speciation. The theory of punctuated equilibrium states that evolutionary change is characterised by short periods of rapid evolution followed by longer periods of stasis in which no change occurs. Despite years of work seeking evidence for punctuational change in the fossil record, the theory remains contentious. Further there is little consensus as to the size of the contribution of punctuational changes to overall evolutionary divergence. Here we review recent developments which show that punctuational evolution is common and widespread in gene sequence data.     

Speciation and the evolution of dispersal along environmental gradients

We analyze the joint evolution of an ecological character and of dispersal distance in asexual and sexual populations inhabiting an environmental gradient. Several interesting phenomena resulting from the evolutionary interplay of these characters are revealed. First, asexual and sexual populations exhibit two analogous evolutionary regimes, in which either speciation in the ecological character occurs in conjunction with evolution of short-range dispersal, or dispersal distance remains high and speciation does not occur. Second, transitions between these two regimes qualitatively differ between asexual and sexual populations, with the former showing speciation with long-range dispersal and the latter showing no speciation with short-range dispersal. Third, a phenotypic gradient following the environmental gradient occurs only in the last case, i.e., for non-speciating sexual populations evolving towards short-range dispersal. Fourth, the transition between the evolutionary regimes of long-range dispersal with no speciation and short-range dispersal with speciation is typically abrupt, mediated by a positive feedback between incipient speciation and the evolution of short-range dispersal. Fifth, even though the model of sexual evolution analyzed here does not permit assortative mating preferences, speciation occurs for a surprisingly wide range of conditions. This illustrates that dispersal evolution is a powerful alternative to preference evolution in enabling spatially distributed sexual populations to respond to frequency-dependent disruptive selection.     

天然水中重金属化学形态研究进展

本文介绍了天然水中溶解重金属的形态及其分析方法,着重介绍了阳极溶出伏安法、原子吸收光谱法等重金属形态分析方法,评价了各种分析方法的优缺点并对其进行了展望。     

Spawning habitat in the spined loach, <Emphasis Type="Italic">Cobitis taenia</Emphasis> (Cypriniformes: Cobitidae)

Spawning habitat of the endangered spined loach Cobitis taenia was studied in northwestern Germany. The distribution of eggs of the loach in the field was best correlated with the density of vegetation but had little correlation with current velocity, water depth, or bottom substrate. In the aquarium, the loach chose dense vegetation for an oviposition site, as inferred by the direct observations of spawning and the location of spawned eggs. It is concluded that such habitat specialization is an important element in the autecology of the endangered fish and a critical stage in the habitat requirements of its populations.     

中国濒危兽类栖息地评估与保护研究进展与展望

目前全球物种正以前所未有的速度灭绝,对野生动物栖息地开展有效的评估与科学的保护是阻止濒危物种走向灭绝,保持其可持续生存与发展的重要前提和手段。本文针对我国的食肉类、有蹄类、灵长类、小型兽类、海洋兽类5个类别的濒危兽类,综述了其栖息地评估与保护研究进展的现状和成果,对相关学术成果进行了归纳与分析,以期为栖息地的科学保护与管理梳理出系统、可供借鉴的研究方法和技术手段,并对其理论和技术的挑战进行了展望,提出了我国濒危兽类栖息地评估和保护研究应走向整体化、定量化、智能化,以及多学科交叉融合应用的“精准化”发展方向,为国家生态建设工程的有效实施提供重要技术支撑。     

Speciation with gene flow and the genetics of habitat transitions

Whether speciation can advance to completion in the face of initially high levels of gene flow is a very controversial topic in evolutionary biology. Extensive gene exchange is generally considered to homogenize populations and counteract divergence. Moreover, the role of introgressive hybridization in evolution remains largely unexplored in animals, particularly in freshwater zooplankton in which allopatric speciation is considered to be the norm. Our work investigates the genetic structure of two young ecological species: the pond species, Daphnia pulex and the lake species, Daphnia pulicaria. Phylogenetic and population genetics analyses were conducted on mitochondrial NADH dehydrogenase 5 (ND5) gene, the nuclear Lactate dehydrogenase (Ldh) gene and 21 nuclear microsatellite markers in 416 individuals from habitats with various degrees of permanence. The strong and consistent phylogenetic discordance between nuclear and mitochondrial markers suggests a complex evolutionary history of multiple independent habitat transition events that involved hybridization and introgression between lake and pond Daphnia. On the other hand, the low level of contemporary gene flow between adjacent populations indicates the presence of effective habitat isolating barriers. The Daphnia system provides strong evidence for a divergence-with-gene flow speciation model that involves multiple habitat transition events.     

高黎贡山冬季白尾梢虹雉运动方式和生境偏好的初步观察

2002及2003年1月,两次对高黎贡山大脑子白尾梢虹雉(Lophophorus sclateri)的运动方式和活动痕迹做了直接观察或样带／样方取样。该鸟滑翔是下行的主要运动方式,上行全为行走;所发现的3个夜宿地均位于坡度大、郁闭度高的近沟谷地带;冬季向低海拔迁移,与降雪有关,使得近沟谷带成为密集利用带。这样的运动和生境利用方式,显然是能耗最小化和觅食效率最大化的行为适应。     

生境破碎化对生物多样性的影响

生境破碎化对生物多样性和生态系统功能的影响是当前国内外生态学家研究的热点问题之一。生境破碎化导致原生境的总面积减小,产生隔离的异质种群,从而影响个体行为特性、种群间基因交换、物种间相互作用及生态过程。生境破碎化的过程引起栖息地内部食物、繁殖场所、局部小气候、边缘效应等生物和非生物条件的变化,从而影响植物种群的大小和灭绝速率、扩散和迁入、遗传和变异以及存活力等,影响动物种群的异质种群动态、适宜生境比例、灭绝阈值、种间关系等。随着景观生态学与农业科学的融合,探索利用景观布局控制害虫发生将是人类利用生境破碎化为人类服务的一条新途径。