Pond-Breeding Amphibian Species Richness and Habitat Selection in a Beaver-Modified Landscape

ABSTRACT Beaver (Castor canadensis) activity creates wetland habitats with varying hydroperiods important in maintaining habitat diversity for pond-breeding amphibians with significantly different breeding habitat requirements. We documented pond-breeding amphibian assemblages in 71 freshwater wetlands in Acadia National Park, Maine, USA. Using 15 variables describing local pond conditions and wetland landscape characteristics, we developed a priori models to predict sites with high amphibian species richness and used model selection with Akaike's Information Criterion to judge the strength of evidence supporting each model. We developed single-species models to predict wood frog (Rana sylvatica), bullfrog (R. catesbeiana), and pickerel frog (R. palustris) breeding site selection. Sites with high species richness were best predicted by 1) connectivity of wetlands in the landscape through stream corridors and 2) wetland modification by beaver. Wood frog breeding habitat was best predicted by temporary hydroperiod, lack of fish, and absence of current beaver activity. Wood frog breeding was present in abandoned beaver wetlands nearly as often as in nonbeaver wetlands. Bullfrog breeding was limited to active beaver wetlands with fish and permanent water. Pickerel frog breeding sites were best predicted by connectivity through stream corridors within the landscape. As beavers have recolonized areas of their former range in North America, they have increased the number and diversity of available breeding sites in the landscape for pond-breeding amphibians. The resulting mosaic of active and abandoned beaver wetlands both supports rich amphibian assemblages and provides suitable breeding habitat for species with differing habitat requirements. Land managers should consider the potential benefits of minimal management of beavers in promoting and conserving amphibian and wetland diversity at a landscape scale.     

The Habitat Amount Hypothesis implies negative effects of habitat fragmentation on species richness

The habitat amount hypothesis (HAH) predicts that species richness in a habitat site increases with the amount of habitat in the ‘local landscape’ defined by an appropriate distance around the site, with no distinct effects of the size of the habitat patch in which the site is located. It has been stated that a consequence of the HAH, if supported, would be that it is unnecessary to consider habitat configuration to predict or manage biodiversity patterns, and that conservation strategies should focus on habitat amount regardless of fragmentation. Here, I assume that the HAH holds and apply the HAH predictions to all habitat sites over entire landscapes that have the same amount of habitat but differ in habitat configuration. By doing so, I show that the HAH actually implies clearly negative effects of habitat fragmentation, and of other spatial configuration changes, on species richness in all or many of the habitat sites in the landscape, and that these habitat configuration effects are distinct from those of habitat amount in the landscape. I further show that, contrary to current interpretations, the HAH is compatible with a steeper slope of the species–area relationship for fragmented than for continuous habitat, and with higher species richness for a single large patch than for several small patches with the same total area (SLOSS). This suggests the need to revise the ways in which the HAH has been interpreted and can be actually tested. The misinterpretation of the HAH has arisen from confounding and overlooking the differences in the spatial scales involved: the individual habitat site at which the HAH gives predictions, the local landscape around an individual site and the landscapes or regions (with multiple habitat sites and different local landscapes) that need to be analysed and managed. The HAH has been erroneously viewed as negating or diminishing the relevance of fragmentation effects, while it actually supports the importance of habitat configuration for biodiversity. I conclude that, even in the cases where the HAH holds, habitat fragmentation and configuration are important for understanding and managing species distributions in the landscape.     

Infanticide in Propithecus diadema edwardsi: An Evaluation of the Sexual Selection Hypothesis

Infanticide might be described as a reproductive strategy employed by anthropoid primate males when they immigrate into new groups. But infanticide has rarely been observed in wild prosimian primates. For the Malagasy lemurs this may reflect one or more of the following: strict breeding seasons; relative monomorphism in canine tooth and body size; small group sizes; male–female dominance relations; and male–female dyads within groups. We addressed the following questions: Do prosimian males commit infanticide in circumstances similar to those in which anthropoids do? and Is there any reproductive advantage for a highly seasonal breeder to commit infanticide? To help answer these questions, we describe the death of a 24-hr-old infant male Propithecus diadema edwardsi from wounds received during a fight between his mother, her adult daughter, and a newly immigrant male. Interbirth intervals between surviving offspring are 2 years for Propithecus diadema edwardsi; therefore, a male could dramatically shorten the time between reproductive windows by killing an infant. Whether this tactic would be favored by sexual selection cannot be addressed until more information has been collected on the length of interbirth interval due to infanticide relative to that of infant death by other causes; how social factors such as stability of breeding relationships affect long-term male reproductive success; how effective female counterstrategies are to prevent infanticide and/or whether they choose to mate with males that commit infanticide; and how often males that kill infants subsequently sire infants, particularly in groups that contain a resident male.     

The Pre-Endosymbiont Hypothesis: A New Perspective on the Origin and Evolution of Mitochondria

Mitochondrial DNA (mtDNA) is unquestionably the remnant of an α-proteobacterial genome, yet only ∼10%–20% of mitochondrial proteins are demonstrably α-proteobacterial in origin (the “α-proteobacterial component,” or APC). The evolutionary ancestry of the non-α-proteobacterial component (NPC) is obscure and not adequately accounted for in current models of mitochondrial origin. I propose that in the host cell that accommodated an α-proteobacterial endosymbiont, much of the NPC was already present, in the form of a membrane-bound metabolic organelle (the premitochondrion) that compartmentalized many of the non-energy-generating functions of the contemporary mitochondrion. I suggest that this organelle also possessed a protein import system and various ion and small-molecule transporters. In such a scenario, an α-proteobacterial endosymbiont could have been converted relatively directly and rapidly into an energy-generating organelle that incorporated the extant metabolic functions of the premitochondrion. This model (the “pre-endosymbiont hypothesis”) effectively represents a synthesis of previous, contending mitochondrial origin hypotheses, with the bulk of the mitochondrial proteome (much of the NPC) having an endogenous origin and the minority component (the APC) having a xenogenous origin.Considering the central role played in all eukaryotic cells by mitochondria or mitochondrion-related organelles (MROs, such as hydrogenosomes and mitosomes) (Hjort et al. 2010; Shiflett and Johnson 2010; Müller et al. 2012), the question of the origin and subsequent evolution of the mitochondrion has long captivated and challenged biologists. In a recent article in this series (Gray 2012), I discussed in detail several aspects of mitochondrial evolution, focusing particularly on how well the accumulating molecular data can be accommodated in current models of mitochondrial origin. In this context, the origin and evolution of the mitochondrial proteome, as opposed to the origin and evolution of the mitochondrial genome, were examined from the perspective of comparative mitochondrial proteomics. Somewhat disconcertingly, as more data have become available, we find ourselves considerably less certain about key aspects of how mitochondria originated than we were (or thought we were) several decades ago.Here, I summarize key points discussed in more detail in the previous article before presenting a novel perspective on how the mitochondrion might have originated. The new model proposed here, which represents a synthesis of both endogenous (“origin from within”) and xenogenous (“origin from outside”) modes, is advanced in an attempt to account for the inability of a purely endosymbiotic model, whose strongest support has come from studies of the mitochondrial genome, to adequately accommodate data on the mitochondrial proteome.     

The Intermediate Disturbance Hypothesis of Species Coexistence Is Based on Patch Dynamics

The 'Intermediate Disturbance Hypothesis' (IDH) is one mechanism suggested to explain indefinite species coexistence. Hutchinson's original concept of the IDH was of a mechanism based on patch dynamics, and logical consideration shows that IDH works only if interpreted this way. Dependence on patch dynamics distinguishes IDH from Gradual Climate Change (GCC), though they are distinct also in terms of premature death of individuals, species selectivity, and the suddenness and transience of the perturbation. The application of the concepts of 'disturbance' and of IDH to phytoplankton communities is questioned.     

Misclassified Resource Selection: Compositional Analysis and Unused Habitat

Abstract: During the past decade, compositional analysis (CA) has been used widely in animal—habitat and resource selection studies. Despite this popularity, CA has not been tested for potential systematic biases such as incorrect identification of preferred resources. We used computer-simulated data based on known habitat use and availability parameters to assess the potential for CA to incorrectly identify preferred habitat use. We consider in particular the situation when available habitat categories not used by all animals are included in the resource selection analysis, with substitution of a relatively small value, such as 0.01, for each 0% utilization value. Progressively larger misclassification-error*** rates in preferred habitat use resulted from substituting progressively smaller positive values for each 0% utilization of a habitat category.     

Lipoatrophia semicircularis: An Electromagnetic Hypothesis

The medical literature describes Lipoatrophia semicircularis (L.s.) as a rare, idiopathic condition characterized by semicircular impressions of the skin, at the front and sides of both thighs. A few years ago, L.s. was diagnosed in hundreds of people, mainly women, among the administrative personnel of two large companies in Belgium. Afterwards, other cases were reported to us in numerous other companies, also in other countries including the Netherlands, France, the United Kingdom, Germany, and Italy. L.s. is thus not as uncommon as previously thought and apparently seems to become an important job‐related illness. We investigated the occurrence and cause of Lipoatrophia semicircularis by registering all recently known cases and paying particular attention to the working conditions of the persons with L.s. Following the elaboration of a working hypothesis, a number of measures were taken inside offices in an attempt to prevent new cases and/or obtain remissions. Some measurements were also performed with regard to the electromagnetic environment of the workplaces. Lipoatrophia semicircularis occurs preferentially in administrative female personnel working in new or renovated office buildings. All afflicted persons work with computers or are at least working in the proximity of electrical devices. It soon became evident that this electric environment plays a major role in the occurrence of L.s., although other factors (e.g., inadequate sitting posture and dry ambient air) may further facilitate L.s. According to our observations, L.s. finds its origin in the electromagnetic environment of work places. It apparently occurs as a result of galvanic coupling between charged materials and the body.     

The Lesser Snow Goose on Wrangel Island: Trophic Interactions with Ruminants and Breeding Habitat Selection

The lesser snow goose (Anser caerulescens caerulescens) has been exterminated across a vast area of Eurasia. At present, it is unable to regenerate there, though its population in North America has reached fifteen million. In Eurasia, the only major nesting colony still persists on Wrangel Island, where the geese use the trophic resources together with ruminants. An assessment of the competitive networks and the trophic interactions between the geese and the ruminants was performed. The analysis of the significance of the trophic niche overlap and the competitive advantages of geese in the habitat preferences has proved that the ruminants are stronger competitors for trophic resources than the geese. It has been ascertained that the levels of competition for trophic resources and/or resource shortages are higher across the habitats of most types associated with the goose colony. The level of the competition for trophic resources is lower, and the feed resources are more diverse and abundant in the habitats that are used by the geese after leaving the colony. It can be concluded that the shortage of resources and/or the stronger competitors for trophic resources (the ruminants) cannot prevent restoration of extinct colonies or the formation of new colonies with a recent increase in the size of the goose population on Wrangel Island. The distribution, abundance, and quality of trophic resources and the competition for them with ruminants do not determine the goose choice of a habitat for a nesting colony. The choice depends on the microclimate and, probably, on a range of other factors.     

动物生境选择研究中的时空尺度

尺度研究已成为生态学上的一个重要概念和研究热点,但是在动物生境选择的研究中尚未引起足够的重视。动物的生境选择包括多层次的判别和一系列等级序位,在各个尺度和水平上具有不同的特征和机制,受到时空尺度的严格限定。繁殖期的时间限制、社群压力、环境变化、动物生理需求的变化决定了动物生境选择的时间制约性;而生境资源的斑块化分布、功能生境之间的相互作用决定了动物生境选择的空间制约性。研究者对时间和空间尺度的选取与应用会直接影响到生境选择研究结果的科学性和实效性。本文从动物生境选择的时空制约性出发,分析了生境选择研究中时间尺度的重要性,叙述了国内外生境选择研究中常见的研究尺度,强调了多尺度研究和长期生态研究的必要性,尺度的选择应该成为生境选择研究的起点和基础。     

The Influence of Mitigation on Sage-Grouse Habitat Selection within an Energy Development Field

Growing global energy demands ensure the continued growth of energy development. Energy development in wildlife areas can significantly impact wildlife populations. Efforts to mitigate development impacts to wildlife are on-going, but the effectiveness of such efforts is seldom monitored or assessed. Greater sage-grouse (Centrocercus urophasianus) are sensitive to energy development and likely serve as an effective umbrella species for other sagebrush-steppe obligate wildlife. We assessed the response of birds within an energy development area before and after the implementation of mitigation action. Additionally, we quantified changes in habitat distribution and abundance in pre- and post-mitigation landscapes. Sage-grouse avoidance of energy development at large spatial scales is well documented. We limited our research to directly within an energy development field in order to assess the influence of mitigation in close proximity to energy infrastructure. We used nest-location data (n = 488) within an energy development field to develop habitat selection models using logistic regression on data from 4 years of research prior to mitigation and for 4 years following the implementation of extensive mitigation efforts (e.g., decreased activity, buried powerlines). The post-mitigation habitat selection models indicated less avoidance of wells (well density β = 0.18 ± 0.08) than the pre-mitigation models (well density β = -0.09 ± 0.11). However, birds still avoided areas of high well density and nests were not found in areas with greater than 4 wells per km² and the majority of nests (63%) were located in areas with ≤ 1 well per km². Several other model coefficients differed between the two time periods and indicated stronger selection for sagebrush (pre-mitigation β = 0.30 ± 0.09; post-mitigation β = 0.82 ± 0.08) and less avoidance of rugged terrain (pre-mitigation β = -0.35 ± 0.12; post-mitigation β = -0.05 ± 0.09). Mitigation efforts implemented may be responsible for the measurable improvement in sage-grouse nesting habitats within the development area. However, we cannot reject alternative hypotheses concerning the influence of population density and intraspecific competition. Additionally, we were unable to assess the actual fitness consequences of mitigation or the source-sink dynamics of the habitats. We compared the pre-mitigation and post-mitigation models predicted as maps with habitats ranked from low to high relative probability of use (equal-area bins: 1 – 5). We found more improvement in habitat rank between the two time periods around mitigated wells compared to non-mitigated wells. Informed mitigation within energy development fields could help improve habitats within the field. We recommend that any mitigation effort include well-informed plans to monitor the effectiveness of the implemented mitigation actions that assess both habitat use and relevant fitness parameters.     

Propagule Limitation,Disparate Habitat Quality,and Variation in Phenotypic Selection at a Local Species Range Boundary

Adaptation to novel conditions beyond current range boundaries requires the presence of suitable sites within dispersal range, but may be impeded when emigrants encounter poor habitat and sharply different selection pressures. We investigated fine-scale spatial heterogeneity in ecological dynamics and selection at a local population boundary of the annual plant Gilia tricolor. In two years, we planted G. tricolor seeds in core habitat, margin habitat at the edge of the local range, and exterior habitat in order to measure spatial and temporal variation in habitat quality, opportunity for selection, and selection on phenotypic traits. We found a striking decline in average habitat quality with distance from the population core, yet some migrant seeds were successful in suitable, unoccupied microsites at and beyond the range boundary. Total and direct selection on four out of five measured phenotypic traits varied across habitat zones, as well as between years. Moreover, the margin habitat often exerted unique selection pressures that were not intermediate between core and exterior habitats. This study reveals that a combination of ecological and evolutionary forces, including propagule limitation, variation in habitat quality and spatial heterogeneity in phenotypic selection may reduce opportunities for adaptive range expansion, even across a very local population boundary.     

Experiential Key Species for Nature-disconnected Generations: An Expert-based Framework for Their A-priori Selection

In urbanized contexts, a progressive disconnection from nature, mainly experienced by the youngest generation, is evident. In this sense, detection of species more suitable for a nature-related experience becomes of primary importance to increase pro-environmental behaviors in children. Here, we propose a simple, quick, and explorative procedure for selecting a set of Experiential Key Species (EKS). Two practical examples are provided for two contexts (a urban park and a suburban wetland) where a large amount of data on vertebrate animal species are available. Depending on their density and eco-behavioral features, each species stimulates different experiences, here considered as a product of intensity and frequency of occurrence. Therefore, for each species we calculated an Experiential Magnitude score on a three-level scale with an expert-based method. We obtained 14 EKS in the urban park site (18% of total) and 18 EKS in the suburban wetland site (9.4%). We observed that in both sites EKS mainly include: (i) heterotherm species (mainly, fishes, amphibians, and water-related reptiles) and (ii) non-native species (about 36% in the urban park and about 17% in the suburban wetland). This information suggests that (i) following a conservation zoning approach, lakes, streams, and their shores may be considered the best experiential sites for children, and (ii) in conservation measures aimed to improve experience and pro-environmental behaviors in younger generations, the role of non-native species (that are of low or null conservation interest) might be relevant. In-deed, individuals of these species (i) are easily detectable, and (ii) may be collected, handled, and farmed with a limited (or absent) impact on biodiversity. In many anthropized contexts, these are the only species that can provide nature experience for younger generations. Based on our observations, we recommend practitioners (i) to adopt the procedure of EKS selection in critical contexts, also adding further regime attributes (area utilized, seasonal duration) to calculate the experiential magnitude score, and (ii) to test the effectiveness of this selection in conservation education projects.     

Crustacean Species Richness in Temporary Pools: Relationships with Habitat Traits

We examined species richness separately for cladocerans and ostracods in 52 temporary pools in a small geographical area, relating species richness with habitat traits using multiple regressions. Habitat traits considered included surface area, water depth, permanence and sediment depth. Permanence was an important predictor of species richness of both cladocerans and ostracods. Additionally, variation in ostracod species richness was significantly explained by water depth (negative relationship) and sediment depth (positive relationship). Surface area was not a statistically significant factor in any of our analyses. The importance of permanence supports the hypothesis that extinction due to pool drying is a major driving force behind the structuring of microcrustacean communities in temporary pools.     

The Gregarine Infection in Different Species of Odonata from the Same Habitat

A qualitative and quantitative study of eugregarine parasites in different dragonfly species was performed around a breeding site at Bergen (Western Norway). Dragonfly larvae were never found to harbour gregarines. As a general rule, the number of dragonflies infected and the number of gregarines present in each individual host increased during the flying season. In the zygopterans Coenagrion hastulatum (Charp.), Enallagma cyathi-gerum (Charp.), and Pyrrhosoma nymphula (Sulz.), the majority became heavily infected. Discoloured, feeble specimens captured in the field exhibited extensive damage to the midgut, probably progressing to bacterial septicaemia. The histopathology of the midgut wall has been recorded from scarcely visible alterations to massive disruption of the epithelium. In these species, gregarine infection apparently reduced the longevity of adults. The population of Lestes sponsa (Hansem.) was moderately infected and injuries of the midgut seldom occurred. In the only infected anisopteran, Sympetrum danae (Sulz.), gregarines seemed unimportant and caused no damage to their hosts. Each gregarine species seemed to thrive in several dragonfly hosts, and a host could harbour at least two different gregarine species at the same time. The pattern of infection is discussed against the background of climatic and edaphic conditions.     

The Effect of Adult Aggression on Habitat Selection by Settlers of Two Coral-Dwelling Damselfishes

Coral-reef fishes experience a major challenge when facing settlement in a multi-threat environment, within which, using settlement cues, they need to select a suitable site. Studies in laboratories and artificial setups have shown that the presence of conspecific adults often serves as a positive settlement cue, whose value is explained by the increased survival of juveniles in an already proven fit environment. However, settlement in already inhabited corals may expose the recruits to adult aggression. Daily observations and manipulation experiments were used in the present study, which was conducted in the natural reef. We revealed differential strategies of settlers, which do not necessarily join conspecific adults. Dascyllus aruanus prefer to settle near (not with) their aggressive adults, and to join them only after gaining in size; whereas Dascyllus marginatus settlers in densely populated reefs settle independently of their adult distribution. Our results present different solutions to the challenges faced by fish recruits while selecting their microhabitat, and emphasize the complexity of habitat selection by the naïve settlers. Although laboratory experiments are important to the understanding of fish habitat selection, further studies in natural habitats are essential in order to elucidate the actual patterns of settlement and habitat selection, which are crucial for the survival of coral-reef fish populations.     

Habitat Selection by the Spur-thighed Tortoise Testudo graeca in a Multisuccessional Landscape: Implications for Habitat Management

As a result of human activities, natural Mediterranean landscapes (including agro-ecosystems) are characterised by a mosaic-like structure with habitat-patches at different successional stages. These systems have high biodiversity levels and are home to a large number of species protected by European laws whose habitats should be adequately managed. In the present work, we study habitat use from an applied point of view in the spur-thighed tortoise Testudo graeca, an endangered reptile present in semi-arid Mediterranean agro-ecosystems. Results show that, at a landscape scale, the species selects simplified vegetation structures and includes in its home range re-colonisation shrubland and small non-irrigated fields. Within the home range, habitat selection patterns vary and areas with higher vegetation cover and complexity are selected. Detected patterns are discussed in terms of the ecological requirements of the species and with a hierarchical view of resources and conditions. The implications of our findings for habitat management aimed at the conservation of the species are also discussed.     

高黎贡山羚牛生境选择初步研究

2004年1月~2005年12月,在高黎贡山自然保护区内开展了羚牛指名亚种的生境调查研究,在调查点内对与羚牛生存有关的生境因子(植被型、郁闭度、坡向、坡位、水源、人为干扰、距主要公路距离、距农用地距离)进行了调查统计。在研究中,将这些生态因子分别分成了3个等级进行回归分析,建立羚牛在不同生境中出现概率的预测方程,通过分析后发现,影响高黎贡山羚牛生境选择的主要生态因子是人为干扰和隐蔽条件,其次是距农业用地距离、距主要公路距离和水源,坡度、坡向和植被型对羚牛生境选择的影响不明显。