Microhabitat Structure Research Articles

Ecomorphological associations of scapulocoracoid form in Greater Antillean Anolis lizards

External morphological metrics have featured prominently in comparative studies examining the morphological convergence that characterizes anoline ecomorphs. To what degree the appendicular-skeletal morphology of Greater Antillean island Anolis lizards tracks their diversity and ecological adaptation, however, remains relatively unexplored. Here we employ computed tomographic scanning techniques to visualize in situ the scapulocoracoid of ecomorph representatives (trunk-ground, trunk-crown, crown-giant, twig) from three islands (Jamaica, Hispaniola, and Puerto Rico), and compare its three-dimensional geometry using qualitative-descriptive and quantitative-morphometric techniques. In contrast to our previous, similarly-conducted study of the pelvic girdle of these same species, the form of the scapulocoracoid varies markedly both within and between species, with much of the variation relating to phylogenetic relationship, specimen size, and assigned ecomorph category. Morphometric variation that correlates with size and/or phylogenetic signal varies between species and cannot be eliminated from the data set without markedly reducing its overall variability. The discovered patterns of skeletal variation are consistent with the demands of locomotor mechanics imposed by the structural configuration of the microhabitat of these ecomorphs. Most pertinently the ecomorphs differ in the anteroposterior length of the coracoid, the dorsoventral height of the scapulocoracoid, the dorsoventral height of the scapula in relation to the height of the suprascapula, and the relative positioning of the borders of the scapulocoracoid fenestra. In the examined ecomorph categories these skeletal differences likely relate to microhabitat usage by permitting different degrees of tilting and displacement of the scapulocoracoid in the parasagittal plane and influencing the sizes of muscle origins and the vectors of their actions. These differences relate to the amount of humeral adduction applied during its protraction, and to the structural stability of the shoulder girdle during acrobatic maneuvers, thus influencing the perch diameter that can be effectively negotiated, a critical factor in the microhabitat structure of Anolis ecomorphs.

Habitat use and microhabitat selection of two lizard species with different niche requirements in a resource availability gradient

ABSTRACT Human alteration toward environment modifies the spatial distribution of available resources that influences habitat selection in animals. Thus, it is necessary to identify the resources that determine species occurrence in modified landscapes to provide the basis for future conservation efforts. We evaluated the habitat use and microhabitat selection of two lizard species with different niche requirements in a resource availability gradient caused by disturbance. Surveys were conducted in El Cielo Biosphere Reserve, Mexico, during 2016 and 2017. The gradient was grouped in four environmental types in the function of climatic (temperature and humidity) and structural variables (included different measures of soil, substrate, and vegetation coverage). For each lizard, 11 variables related to the microhabitat structure were recorded. Microhabitat selection for each environment type along the gradient was determined and compared via discriminant analysis. The results showed that Sceloporus variabilis, a species that uses a wide range of resources, can select different microhabitats along the gradient; while Lepidophyma sylvaticum, a species with a restricted use of resources, select microhabitats with similar specific characteristics and avoided disturbed areas with scarce canopy cover. This differential response was related to the degree of specificity in resources selection and physiological restrictions of each species.

Population asynchrony alone does not explain stability in species-rich soil animal assemblages: The stabilizing role of forest age on oribatid mite communities.

The importance of microbial and plant communities in the control of the diversity and structure of soil animal communities has been clarified over the last decade. Previous research focused on abiotic factors, niche separation and spatial patterns. Significant gaps still exist in our knowledge of the factors that control the stability of these communities over time. We analysed a 9-year dataset from the national Long-term Ecological Research Network of Latvia. We focused on 117 oribatid species from three Scots pine forests of different age (<40, 65 and >150years) and structure. For each forest type, 100 samples were collected each year, providing very high replication and long time series for a soil community. We assessed different aspects of stability: we used a dynamic null model, parameterized on observed growth rates, to test the hypothesis that asynchrony in species populations stabilizes total community size; we also analysed alpha and beta diversity over time to test the hypothesis that temporal variation in species composition and relative abundances is controlled by forest attributes. Real communities can be more stable than their stochastic counterparts if species are asynchronous, confirming for the first time the role of asynchrony in stabilizing soil communities. Yet, while some real communities were more stable and had higher abundance and growth rates than others, they were not necessarily more asynchronous than the less stable communities. Species composition and relative abundances were also less variable in the more stable communities. Species asynchrony generally stabilizes species-rich communities but is not sufficient to explain the different levels of stability between forests. Forest age is a key factor explaining the different levels of overyielding and so stability. Data suggest that both asynchrony and high diversity of microhabitat structure of Scots pine forests promote the stability of soil animal communities.

Variation in Helminth Parasite Component Communities of Gambusia affinis.

In north-central Texas streams, seasonal changes in ambient temperature and rainfall result in dynamic variation in microhabitat structure, affecting the distribution and abundance of hosts. Since the complex life cycles of parasites require the presence and interaction of multiple hosts, the seasonal variations in microhabitats could influence parasite component communities within these ecosystems. Gambusia affinis (western mosquitofish) serves as a host for a variety of larval and adult parasites. Factors that affect helminth component communities in populations of mosquitofish from the Paluxy River were investigated in this study. Gambusia affinis individuals were collected from 3 sites monthly from June 2015 through August 2016. All helminth parasites were collected during necropsy and subsequently identified. From 495 mosquitofish, 5,283 helminths were collected. Component community diversity varied among collection sites and collection dates and was positively influenced by river flow. These results indicate that helminth assemblages infecting mosquitofish in the Paluxy River vary through time and space, as well as in response to environmental variation (i.e., changes in water flow).

Responses of Rotifer Community to Microhabitat Changes Caused by Summer-Concentrated Rainfall in a Shallow Reservoir, South Korea

Empirical studies suggest that the structural heterogeneity of aquatic ecosystem microhabitat is determined by the diversity and abundance of macrophytes. However, excessive accumulation of free-floating macrophytes on the water surface can reduce the biomass of submerged macrophytes, resulting in a relatively simplified habitat structure. We hypothesized that heavy summer rainfall disrupts the growth of free-floating macrophytes covering much of the Jangcheok Reservoir’s water surface, thereby resulting in a more complex habitat structure by allowing development of a more diverse of macrophytic community. We divided long-term (2008–2017) monitoring data (rainfall, macrophytes, and rotifers) into two groups: Rainy and Dry years, corresponding to years with annual rainfall higher and lower than the total annual average, respectively. We found that summer densities of rotifers fell sharply in Rainy years, but increased continuously in Dry years. This trend resulted in greater autumn densities in Rainy relative to Dry years, which we attributed to changes in habitat related to differential macrophyte development. Moderate disturbance of the water surface caused by high summer rainfall can promote growth of submerged macrophytes by creating large areas of open water and therefore a more complex autumnal microhabitat structure, resulting in seasonal variations in rotifer community structures and populations. Moreover, a highly complex microhabitat structure restricts foraging activity of fish (i.e., Lepomis macrochirus) that prey on rotifers. Based on these findings, we suggest that summer-concentrated rainfall plays an important role in supporting the density and species diversity of rotifers.

Facultative mutualism increases survival of an endangered ant-tended butterfly

Much of our understanding of mutualism is derived from pairwise obligate interactions between specialized participants. These observations may not adequately inform conservation efforts for facultative mutualist species, especially for areas in which invasive species are present and affect the mutualism. We evaluate the effects of ant attendance on larval survival for the endangered Fender’s blue butterfly (Icaricia icarioides fenderi Macy) in situ and examine the effects of biotic and abiotic factors—specifically ant community composition and microhabitat structure—on this mutualistic interaction in Oregon, USA. Fender’s blue larval survival was as much as three times higher in plots with a high proportion of ant attendance compared to plots in which larvae were rarely tended, and ant recruitment was reduced by dense, invasive European grasses. Thatch from these dense invasives, specifically tall oatgrass (Arrhenatherum elatius Beauv.) and tall fescue (Schedonorus arundinaceus Schreb.), are a threat to larval survival. In addition, variation in microhabitat structure determined which ant species occurred in our plots. Larvae were associated with ten ant species but primarily tended by only two: Prenolepis imparis Say and Aphaenogaster occidentalis Emery, and we observed no difference in butterfly larval survival between the two predominant ant species. Conservation efforts for this species would benefit from actions that reduce invasive grasses and facilitate ant tending interactions. Our study demonstrates how invasive grasses and forbs in degraded prairie systems can negatively impact the conservation of an at-risk species by disrupting an important mutualistic interaction.

Habitat use, interspecific competition and phylogenetic history shape the evolution of claw and toepad morphology in Lesser Antillean anoles

AbstractEcologically functional traits are the product of several, at times opposing, selective forces. Thus, ecomorphological patterns can be disrupted locally by biotic interactions, such as competition, and may not be consistent across lineages. Here, we studied the evolution of claws and toepads in relationship to macrohabitat (vegetation), use of structural microhabitat (perch height) and congeneric competition for two distantly related Lesser Antillean anole clades: the Anolis bimaculatus and Anolis roquet series. We collected univariate and geometric morphometric data from 254 individuals across 22 species to test the hypotheses that functional morphology should covary with both vegetation and perch height and that the presence of a competitor may disrupt such covariation. Our data showed predictable associations between morphology and macrohabitat on single-species islands but not when a congeneric competitor was present. The outcomes of competition differed between series, however. In the A. bimaculatus series, species with a sympatric congener diverged in claw and toepad traits consistent with functional predictions, whereas A. roquet series anoles showed either no association between habitat and morphology or the opposite pattern. Our results demonstrated that ecomorphological patterns across macrohabitats can be disrupted by competition-driven microhabitat partitioning and that specific morphological responses to similar ecological pressures can vary between lineages.

Types of Leaves Preference by Kalophrynus palmatissimus in Two Forest Reserves

A collection of leaves was carried out at each captured area of Kalophrynus palmatissimus in Ayer Hitam Forest Reserve (AHFR), Selangor and Pasoh Forest Reserve (PFR), Negeri Sembilan. K. palmatissimus is a leaf litter frog. Leaves or leaf litter provide microhabitat structures for leaf litter frogs. Leaves or leaf litter offer retreat sites for leaf litter frogs and shelters for their food sources (i.e. diversity of invertebrates). However, there have been little discussions about the types of leaves as the microhabitat structure of K. palmatissimus. The objective of this study was to investigate the types of leaves that were highly adapted by K. palmatissimus at both forest reserves. Thirty four and thirty one quadrats (2m × 2m) were established in AHFR and PFR respectively for a collection of leaves. A total of 53 and 85 leaves were recorded at AHFR and PFR respectively. Most of the leaves that were collected at both forest reserves were non-hairy/smooth leaves. The data collections in AHFR and PFR have significantly contribute to better understanding of types of leaves as the most suitable habitat and foraging sites for K. palmatissimus.

Heterogeneous forest structures favor persistence of the grassland Mediterranean geophyte Gagea lacaitae

ABSTRACTLand use changes in the northern Mediterranean basin threaten our ability to conserve its habitats and species. Reduced grazing has led to local declines in grassland species and colonization by forest species leading to conservation actions aimed at restoring open habitats. Recently, populations of Gagea lacaitae, a bulbous species typical of Mediterranean open xeric grasslands, have been discovered in forest clearings, an unexpected habitat for this species. Here, we surveyed 48 plots to characterize and compare the ecological niche of G. lacaitae growing in both open xeric and forest clearing habitats. We recorded floristic composition and plant cover and collected soil samples to measure water retention capacity, pH, organic matters and conductivity. Open xeric grasslands and forest clearings differ in plant cover, community composition, and microhabitat structure but not in plant diversity, mean soil conditions, or G. lacaitae cover. Key similarities in conditions allow this species to persist in woodlands that heterogenous enough to include clearings. Such habitats have value for conserving this species and should be sustained.

Microhabitat Utilisation of Endemic Lizard Calotes nigrilabris in the Grasslands of Horton Plains National Park, Sri Lanka

The endemic endangered agamid lizard Calotes nigrilabris inhabits the grasslands of Horton Plains National Park (HPNP) and it is restricted to a few localities in the central highlands of Sri Lanka. In this study, the microhabitat utilisation of Calotes nigrilabris was investigated utilising line transects and quadrate method. The comparison of available microhabitat variables with occupied microhabitat variables revealed that there was a significant difference between some of the variables (Man-Whiteney U test, p&lt;0.05) indicating that C. nigrilabris was selective in its microhabitat utilisation. Based on PCA analysis, amount and type of vegetation was the main determining factor of microhabitat preference of this species. Ulex sp. cover (PC1, 0.606) and Rhododendron sp. cover (PC2,-0.603) were significantly affecting the occupied microhabitat structure. Microhabitat utilisation varied in the temporal and spatial scales also indicating clear resource partitioning between different maturity stages. The results of this study indicate that C. nigrilabris actively selects and utilises the most suitable grassland microhabitats of HPNP and provide important insights for the conservation and management of the species as well as its natural habitat.

A sea of tentacles: optically discernible traits resolved from planktonic organisms in situ

Abstract Trait-based simplifications of plankton community structure require accurate assessment of trait values as expressed in situ. Yet planktonic organisms live suspended in a fluid medium and often bear elongate appendages, delicate feeding structures, and mucous houses that are badly damaged upon capture or removal from the fluid environment. Fixatives further distort organisms. In situ imaging of zooplankton from a fully autonomous Zooglider reveals a suite of trait characteristics that often differ markedly from those inferred from conventionally sampled plankton. In situ images show fragile feeding appendages in natural hunting postures, including reticulate networks of rhizopods, feeding tentacles of cnidarians, and tentilla of ctenophores; defensive spines and setae of copepods; intact mucous houses of appendicularians; and other structures that are not discernible in conventionally collected zooplankton. Postures characteristic of dormant copepods can be identified and the presence of egg sacs detected. Intact, elongate diatom chains that are much longer than measured in sampled specimens are resolvable in situ. The ability to image marine snow, as well as small-scale fluid deformations, reveals micro-habitat structure that may alter organismal behaviour. Trait-based representations of planktonic organisms in biogeochemical cycles need to consider naturally occurring traits expressed by freely suspended planktonic organisms in situ.

Microhabitat Factors Influenced the Prevalence of Pathogenic Leptospira spp. in Small Mammal Host.

Leptospirosis, a widespread zoonotic disease, is a public health problem, especially in major urban centres, and is mainly reported to be associated with rats. In Malaysia, focus has been primarily given to the Leptospira prevalence in rodents per se, but there is lack of information on the microhabitat structure of the outbreak areas. We aimed to determine the diversity of small mammal species, microhabitat types, and their prevalence of pathogenic Leptospira spp. in the outbreak areas, which were categorized as urban, semi-urban, and recreational forests. Sampling involved deploying 100 to 300 live traps at each study site. Kidney samples were extracted from selected individuals, for screening of pathogenic Leptospira spp. by PCR. Out of 537 individuals from 15 small mammal species captured, 4 species were recorded from urban, 13 from semi-urban, and 11 from recreational forest sites. From 389 individuals screened, 58 were tested positive for pathogenic Leptospira. Recreational forests recorded the highest prevalence with 19.4% (n = 93), followed by urban, 16.6% (n = 163) and semi-urban sites with 9.8% (n = 133). Seven rodent species were tested positive for pathogenic Leptospira from all areas. R. norvegicus was found to harbour the highest prevalence (66.7%) in urban, R. rattus (53.8%) in semi-urban, whereby M. whiteheadi (44.4%) in recreational forest sites. Microhabitat analysis revealed that rubbish quantity contributed especially strongly to a high prevalence of Leptospira. This study contributes to understanding of the host and microhabitat preferences of Leptospira, which is important in controlling the spread of this disease in human's landscapes.

The ecological signal on the shape of the lacertid vestibular system: simple versus complex microhabitats

Shape variation in the vestibular system is often linked to microhabitat structure and locomotor performance. Highly circular and orthogonal semicircular canal pairs are linked to higher motion sensitivity. Here, we use 3D geometric morphometrics to investigate shape variation in the vestibular system within lacertid lizards and its relationship to balance control. We found that lacertids living in complex microhabitats possess narrow but longer vestibular systems, an S-shaped anterior canal, a straightened lateral canal and a short common crus. However, lacertids specialized for simple microhabitats (open areas) possess wider but shorter vestibular systems, more circular anterior and lateral canals, and a longer common crus. Contrary to our expectations, species living in simple microhabitats possess more anatomical adaptations that enhance the sensitivity of their vestibular system. This suggests that species inhabiting open areas may benefit from increased sensitivity given that they are potentially more visibile to predators and have lower shelter availability. Finally, the wider shape of the vestibular system of the open area species may be linked to a wider and potentially flattened skull, which may be related to sand-diving or prey hardness.

High microhabitat heterogeneity drives high functional traits in forest birds in five protected forest areas in the urban mosaic of Durban, South Africa

Anthropogenic forest disturbance poses a significant threat to the persistence of wildlife. Generally, disturbance of forest environments alters vegetation structure, affecting specialised niche-dependent avian species. We investigated the influence of a comprehensive suite of vegetation structures on the taxonomic and functional diversity of avian forest species in five protected forest areas in the urban mosaic of eThekwini Municipality, Durban, South Africa during the austral breeding season of 2016. We conducted 135 fixed-radius point-count surveys between the vegetation classes of Indigenous Forest (IF) and Coastal Thicket/Dense Bush (TDB; a secondary wooded-habitat that represents regenerating Indigenous Forest), and recorded microhabitat structure covariates at each survey site. We conducted RLQ analyses to examine the association between avian functional traits and microhabitat structures present at each survey site. There was no significant difference in vegetation structure nor species richness between IF and TDB. Species with specialised ecological niches (e.g. large-bodied frugivores; small-bodied insectivores, cavity-nesters) were present in both IF and TDB, indicating that TDB in Durban represents an advanced stage of forest regeneration. We highlight the importance of both IF and TDB for providing critical habitat for both avian generalised and specialised functional traits in the forest patches in the urban mosaic. Crucially, we show that forested areas under conservation management in urbanised areas successfully provide species with a wide variety of functional traits critical to ecosystem functioning and human health.

Drivers of Psammodromus algirus abundance in a Mediterranean agroforestry landscape

Mediterranean European landscapes have been shaped by human activities for centuries, particularly by livestock and farming. Traditionally managed montado landscapes have been recognized as having a crucial role in biodiversity conservation, providing habitat complexity and thus, ecological conditions for a variety of species. Biodiversity associated with montado can only be maintained under specific agricultural practices, with the intensification or abandonment of such practices posing serious threats for wildlife. Despite the high number of reptile species endemic to the Iberian Peninsula, research on the influence of agroforestry management practices on these species has been scarce. The mediterranean lizard Psammodromus algirus is a generalist species that responds to changes in the structure and quality of microhabitats, specifically the shrub layer, which is greatly affects by changes in cattle grazing intensity. In this study, we assessed how grazing affects the frequency of occurrence of P. algirus in a Mediterranean landscape dominated by montado. We detected that areas of intermediate age regarding grazing exclusion support higher lizard abundance, with P. algirus abundance being limited by vegetation structure and solar radiation. Thus, we may infer that the vegetation structure regulatory role of cattle will affect this lizard’s abundance, limiting it indirectly. We suggest that the maintenance of adequate traditional management, allowing the grazing pressure at low to moderate levels, would be beneficial to this species and reptiles in general and conclude that reconciling grazing and reptile conservation is possible if done in a sustainable way.

Finer‐scale habitat predicts nest survival in grassland birds more than management and landscape: A multi‐scale perspective

Abstract Birds may respond to habitat at multiple scales, ranging from microhabitat structure to landscape composition. North American grassland bird distributions predominantly reside on private lands, and populations have been consistently declining. Many of these lands are enrolled in U.S. federal conservation programmes, and properly guided management policies could alleviate declines. However, more evaluative research is needed on the effects of management policies juxtaposed with other multi‐scale habitat features. Furthermore, research focused on nest survival is arguably more valuable because habitat associations with avian densities can sometimes be deceptive. We investigated nest survival of a grassland facultative (red‐winged blackbird Agelaius phoeniceus) and obligate species (dickcissel Spiza americana), and two nesting communities (ground and above‐ground nesters) relative to management and multi‐scale habitat (nest‐site characteristics, in‐field microhabitat, patch metrics, and landscape context). Our study was conducted on private lands in Illinois (2011–2014) and directly linked to policy‐based management (discing, herbicidal spraying, spray/interseeding) and landowner decisions. Multi‐scale models explained more variation in nest survival compared to single scales or management in three of four analyses (blackbirds, dickcissels, and above‐ground nesters). Finer‐scale habitat variables, such as nest‐site characteristics, were more often in top and among the competitive models relative to landscape factors. Compared with other management types, discing (i.e., tractor‐pulled disc harrows removed approximately 50% of vegetation) displayed distinct effects and positively influenced nest survival in above‐ground nesters. Also, greater proportions of a field managed cumulatively and yearly, regardless of type, generally improved nest survival for dickcissels and above‐ground nesters. All groups except above‐ground nesters had generally higher nest survival in native‐grass dominated fields. Synthesis and applications. Habitat practitioners can improve nest survival for certain grassland birds by directly affecting in‐field microhabitat vegetation and structure. However, characteristics associated with specific nest locations often drive nest survival. We suggest habitat managers and agency staff promote native grass practices and management, such as discing, to enhance nest survival of grassland bird populations. Management will likely be most effective in favourable unfragmented grassland landscapes with less surrounding forested areas, which also promote other important responses (e.g., colonization and persistence) of target species.

Predicting abundance and diversity of tree-related microhabitats in Central European montane forests from common forest attributes

The continued provision of old-growth elements in forest landscapes is a critical factor for biodiversity conservation in Central Europe. A well-established method for predicting the potential of forests to maintain biodiversity is to quantify tree-related microhabitat structures (TreMs). Our aim was to predict the TreM abundance and diversity for collectives of TreM-bearing trees; here 15 large trees per plot that were preselected by the largest crown sizes using remote sensing information. TreMs were inventoried on 2085 living trees across 139 plots (each 1 ha) in montane forests of the Black Forest, southwest Germany according to a detailed catalogue comprising 64 different TreM structures. We tested the influence of forest management, forest cover in the surrounding landscape (25 km radius), forest type, the number of standing dead trees, altitude and mean diameter at breast height (DBH) on the abundance and diversity of TreMs on living trees. All plots are managed or have been recently (20–40 yrs) abandoned from management. Generalized linear models (GLM) were used to identify the drivers of abundance and diversity of TreMs. The abundance of TreMs borne by the 15 large trees per plot is greater on plots located at higher altitudes. Increasing mean DBH leads to significantly higher abundance and diversity of TreMs. Groups of TreM-bearing trees in monospecific coniferous forests have the highest abundance but those in mixed-coniferous-broadleaved forests have the greatest diversity of TreMs. The occurrences of 11 out of 64 specific TreM structures were related to forest management, forest type, altitude or mean DBH. Large branch holes and buttress cavities increased with mean DBH and were found more frequently in mixed-coniferous-broadleaved forests than in the other forest types. The abundance of epiphytes on TreM bearing trees increased with altitude. This study demonstrates that the average abundance and diversity of TreMs can be predicted with readily available forest attributes. Additionally, the occurrence of specific TreMs could be described with the variation in these selected forest attributes.

Avian predation intensity as a driver of clinal variation in colour morph frequency.

Phenotypic variation provides the framework for natural selection to work upon, enabling adaptive evolution. One of the most discernible manifestations of phenotypic variability is colour variation. When this variation is discrete, genetically based colour pattern morphs occur simultaneously within a population. Why and how colour polymorphisms are maintained is an evolutionary puzzle. Several evolutionary drivers have been hypothesized as influencing clinal patterns of morph frequency, with spatial variation in climate and predation being considered especially important. Despite this, no study has examined both of their roles simultaneously. The aims of this study were to: (a) examine the covariation of physiology, environmental variables and colouration at a local scale; and (b) determine if these factors and their interplay explain broad clinal variation in morph frequency. We used the lizard Liopholis whitii as a model system, as this species displays a discrete, heritable polymorphism for colour pattern (plain-backed, patterned morphs) whose morph frequency varies latitudinally. We measured reflectance, field activity temperatures and microhabitat structure to test for differences in crypsis, thermal biology and microhabitat selection of patterned and plain-backed morphs within a single population where colour morphs occur sympatrically. We then used data from the literature to perform a broad-scale analysis to identify whether these factors also explained the latitudinal variation of morph frequency in this species. At the local scale, plain-backed morphs were found to be less cryptic than patterned morphs while no other differences were detected in terms of thermal biology, dorsal reflectance and microhabitat use. At a broader scale, predation was the most influential factor mediating morph frequency across latitudes. However, the observed pattern of morph frequency is opposite to what the modelling results suggest in that the incidence of the least cryptic morph is highest where predation pressure is most severe. Clinal variation in the level of background matching between morphs or the potential reproductive advantage by the plain-backed morph may, instead, be driving the observed morph frequency. Together, these results provide key insights into the evolution of local adaptation as well as the ecological forces involved in driving the dynamics of colour polymorphism.

Microhabitat structure and food availability modelling a small mammal assemblage in restored riparian forest remnants

Abstract Small mammal populations respond to environmental changes in secondary riparian forest remnants in different ways, depending on the influences of biotic and abiotic variables. The present study evaluated how habitat/microhabitat structure and food availability influence small mammal assemblages in restored riparian forest remnants. Pitfall traps disposed in three linear transects were used to collect small mammals during 9 months of field work. General linear models were built to test the hypothesis that microhabitat structure (litter biomass and type – leaves and branches) and food availability (richness of zoochoric tree species and arthropods) influence species richness and abundance of small mammals. Three hundred and eighty-two individuals belonging to 14 species were captured. Biomass and type of litter (leaves or branches) provided greater structural to microhabitats, allowing the coexistence of morphologically similar species. Besides, food availability influenced foraging strategies of marsupials, forcing them to use the forest floor when zoochoric plants were rare. Thus, litter structure and food availability, allowing spatial segregation of the small mammal species using the forest fragments. We concluded that the maintenance of small mammals and their ecosystem services in restored riparian forests are dependent on habitat structure and food availability, thus, litter and zoochoric plants should be conserved in riparian forest fragments, especially those reforested.

Hemlock woolly adelgid invasion affects microhabitat characteristics and small mammal communities

Hemlock woolly adelgid (HWA) invasion and preemptive logging practices alter the habitat structure of New England forests and may indirectly affect associated small mammal communities. Microhabitat structure was measured and small mammals were censused in eight large experimental plots to quantify these effects. The Harvard Forest long-term ecological research experiment is a replicated two-block design that includes four ~ 0.81-ha canopy treatments: (1) hemlock control, (2) hardwood control, (3) girdled Treatment, in which hemlock trees were killed by girdling in 2005 and left standing to simulate HWA invasion, and (4) logged treatment, in which trees were removed to simulate preemptive logging management practices. Nine microhabitat characteristics were measured from plot photos revealing differences among ground and canopy microhabitat structure. Small mammals were censused during high (2012) and low (2013) abundant years. Populations of common species were estimated with mark-recapture analysis. Peromyscus spp. were not affected by treatment in either year, but southern red-backed vole populations were greatest in the girdled treatments in 2012 and rarely captured in 2013. Between 6 and 9 mammal species were recorded in all treatments and species composition varied slightly. Estimated species richness was greater in girdled treatments than hemlock controls, but did not differ between girdled and logged treatments, which suggests preemptive logging is as detrimental to some small mammal species as HWA invasion. Overall, there is little evidence of a major shift in small mammal community structure in response to HWA invasion, with only minor changes in relative abundance both years.