Colonization Of New Habitats Research Articles

The infra-red (IR) landscape of Triatoma infestans. An hypothesis about the role of IR radiation as a cue for Triatominae dispersal

This paper presents the infrared (IR) emission spectrum of hosts and habitats of Triatoma infestans in the chaco region of NW Argentina, representing the first attempt to correlate the natural infrared stimulus with the known behaviour of these blood-sucking insect, vectors of Trypanosoma cruzi – causative agent of Chagas disease. The study was carried out in two rural villages of La Rioja Province (Argentina). A FLYR i40 camera was used to obtain IR pictures which were analyzed to determine the thermal range for humans, domestic animals, building materials, and general background emissions. From sunset to the first hours of night, the thermal contrast between hosts and their landscape rises, increasing the likelihood that hosts could be differentiated by the vector. However, some building materials, can retain high temperatures during the night, which might add attractiveness to the presence of hosts. The results suggest that the most attractive habitats for dispersing bugs would be those at short distance, with high CO2 emission and strong IR radiation indicative of host presence. Goats corrals may be the most attractive habitat to disperse, within the domestic habitat. Dispersal would be favoured in periods of low atmospheric water saturation when IR perception is highest. In the IR band, the potential host and habitat discrimination available for the insects fits well with their known sensory capacities and observed dispersive behavior. Research in this area could be of considerable interest in relation to vector surveillance, epidemiology of Chagas disease transmission, and to develop new methods to minimise triatomine colonisation of new habitats.

Ephemeral Pleistocene woodlands connect the dots for highland rattlesnakes of the Crotalus intermedius group

Aim To test how Pleistocene climatic changes affected diversification of the Crotalus intermedius species complex. Location Highlands of Mexico and the south-western United States (Arizona). Methods We synthesize the matrilineal genealogy based on 2406 base pairs of mitochondrial DNA sequences, fossil-calibrated molecular dating, reconstruction of ancestral geographic ranges, and climate-based modelling of species distributions to evaluate the history of female dispersion. Results The presently fragmented distribution of the C. intermedius group is the result of both Neogene vicariance and Pleistocene pine–oak habitat fragmentation. Most lineages appear to have a Quaternary origin. The Sierra Madre del Sur and northern Sierra Madre Oriental are likely to have been colonized during this time. Species distribution models for the Last Glacial Maximum predict expansions of suitable habitat for taxa in the southern Sierra Madre Occidental and northern Sierra Madre Oriental. Main conclusions Lineage diversification in the C. intermedius group is a consequence of Pleistocene climate cycling. Distribution models for two sister taxa in the northern and southern Sierra Madre Occidental and northern Sierra Madre Oriental during the Last Glacial Maximum provide evidence for the expansion of pine–oak habitat across the Central Mexican Plateau. Downward displacement and subsequent expansions of highland vegetation across Mexico during cooler glacial cycles may have allowed dispersal between highlands, which resulted in contact between previously isolated taxa and the colonization of new habitats.

Migrations of dragonflies (Odonata) in the south of the West Siberian plain

The paper presents a summary of mass dragonfly migrations observed previously in Russia, in particular in West Siberia. From 1969 to 2009, the authors studied the dynamics of dragonfly population, their spatial distribution and movements in the West Siberian forest-steppe. The main studies were conducted in the Lake Chany basin (the Biological Station of the Institute of Animal Systematics and Ecology, Siberian Division, Russian Academy of Sciences). The spatial redistribution of dragonflies is regarded as a balance of homing and wandering behavior. Homing results in a relative stability of local dragonfly populations and assemblages, while wandering leads to dispersal of dragonflies from their emergence sites and colonization of new habitats; the latter is especially important due to the ephemeral nature of many shallow reservoirs where the nymphs develop. The formation of more or less constant migration routes is a peculiar variant of wandering activities. A special type of dragonfly migrations is mass exodus from native habitats, triggered by excessive population growth and leading to elimination of all or most individuals. Such migrations not only optimize the size of dragonfly populations but also facilitate removal of nutrients and organic matter from eutrophic water bodies. An original generalized classification of dragonfly migrations is proposed.

Changes in behavioural trait integration following rapid ecotype divergence in an aquatic isopod

Colonization of new habitats can relax selection pressures, and traits or trait combinations no longer selected for might become reduced or lost. We investigated behavioural differentiation and behavioural trait integration in the freshwater isopod Asellus aquaticus. This isopod has recently colonized a novel habitat and diverged into two ecotypes which encounter different predator faunas. We investigated sex-specific behavioural differences and phenotypic integration in three behavioural assays: (i) time to emerge (TE) from a shelter, (ii) activity and (iii) escape behaviour. General activity and escape behaviour differed between ecotypes. Furthermore, general activity and TE differed between sexes. Behavioural traits were more frequently correlated in the ancestral habitat, and phenotypic integration tended to be higher in this habitat as well. Our study suggests that different predator types, but also other ecological factors such as habitat matrices and population densities, might explain the differences in behavioural integration in these ecotypes.

Return movement of a humpback whale between the Antarctic Peninsula and American Samoa: a seasonal migration record

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 13:117-121 (2011) - DOI: https://doi.org/10.3354/esr00328 NOTE Return movement of a humpback whale between the Antarctic Peninsula and American Samoa: a seasonal migration record Jooke Robbins1,*, Luciano Dalla Rosa2,3,4, Judith M. Allen5, David K. Mattila6, Eduardo R. Secchi2,4, Ari S. Friedlaender7, Peter T. Stevick5, Douglas P. Nowacek7,8, Debbie Steel9 1Provincetown Center for Coastal Studies, 5 Holway Avenue, Provincetown, Massachusetts 02657, USA 2Projeto Baleias/Brazilian Antarctic Program, Museu Oceanográfico ‘Prof. Eliézer C. Rios’, FURG, Rio Grande, RS 96200-970, Brazil 3Department of Zoology and Marine Mammal Research Unit, University of British Columbia, Room 247, AERL, 2202 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada 4Laboratório de Tartarugas e Mamíferos Marinhos/Instituto de Oceanografia, Universidade Federal do Rio Grande-FURG, Cx.P. 474, Rio Grande, RS 96201-900, Brazil 5Antarctic Humpback Whale Catalog, Allied Whale, College of the Atlantic, Bar Harbor, Maine 04609, USA 6Hawaiian Islands Humpback Whale National Marine Sanctuary, 726 S. Kihei Road, Kihei, Hawaii 96753, USA 7Nicholas School of the Environment, and 8Pratt School of Engineering, Duke University Marine Laboratory, 135 Duke Marine Lab Rd., Beaufort, North Carolina 28516, USA 9Marine Mammal Institute, Oregon State University, 2030 SE Marine Science Drive, Newport, Oregon 97366, USA *Email: jrobbins@coastalstudies.org ABSTRACT: Humpback whales Megaptera novaeangliae are seasonal migrants that mate and calve at low latitudes and feed at mid- to high latitudes. Connections between most Southern Hemisphere breeding and feeding areas are not well understood, but are critical for assessing stock structure and human impacts. Photo-identification was performed to identify the feeding grounds of an Endangered sub-population that breeds in the central South Pacific Ocean (CSP). Identification photographs were obtained from 159 ind. at American Samoa and compared to 3508 Southern Hemisphere humpback whales in the Antarctic Humpback Whale Catalogue (AHWC), including 1352 from Antarctic feeding grounds. Two individuals from American Samoa were seen on 3 occasions at the Antarctic Peninsula. This is the first known feeding site for American Samoa and one of few reliably identified for the CSP. AHWC #2950 was confirmed to have undertaken a round-trip movement of no less than 18840 km, spanning 108 longitudinal degrees. This represents the largest mammalian migration known to date and a departure from historical assumptions about CSP migratory patterns. The frequency, causes, and fitness implications of such movements have yet to be determined. However, distance is the only known extrinsic barrier to humpback whale movement within oceans, and so maximum individual range is 1 factor potentially affecting population exchange and colonization of new habitats. The movement documented here may place this Endangered sub-population at risk if conservation efforts are relaxed in unidentified parts of its range. Yet, the ability of humpback whales to undertake such extensive movements may have also contributed to the apparent recovery of some populations versus other historically exploited whale species. KEY WORDS: Migration · Humpback whale · Photo-ID · Spatial distribution · Conservation Full text in pdf format PreviousNextCite this article as: Robbins J, Dalla Rosa L, Allen JM, Mattila DK and others (2011) Return movement of a humpback whale between the Antarctic Peninsula and American Samoa: a seasonal migration record. Endang Species Res 13:117-121. https://doi.org/10.3354/esr00328 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 13, No. 2. Online publication date: January 27, 2011 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2011 Inter-Research.

CRYPTIC GENETIC VARIATION AND BODY SIZE EVOLUTION IN THREESPINE STICKLEBACK

The role of environment as a selective agent is well-established. Environment might also influence evolution by altering the expression of genetic variation associated with phenotypes under selection. Far less is known about this phenomenon, particularly its contribution to evolution in novel environments. We investigated how environment affected the evolvability of body size in the threespine stickleback (Gasterosteus aculeatus). Gasterosteus aculeatus is well suited to addressing this question due to the rapid evolution of smaller size in the numerous freshwater populations established following the colonization of new freshwater habitats by an oceanic ancestor. The repeated, rapid evolution of size following colonization contrasts with the general observation of low phenotypic variation in oceanic stickleback. We reared an oceanic population of stickleback under high and low salinity conditions, mimicking a key component of the ancestral environment, and freshwater colonization, respectively. There was low genetic variation for body size under high salinity, but this variance increased significantly when fish were reared under low salinity. We therefore conclude that oceanic populations harbor the standing genetic variation necessary for the evolution of body size, but that this variation only becomes available to selection upon colonization of a new habitat.

Reproductive parameters of Lobaria pulmonaria (L.) Hoffm. in the Urals

The capacity of species for expansion and colonization of new habitats is a key condition for the maintenance of their populations. In this study, specific features of the reproductive potential have been analyzed in Lobaria pulmonaria populations growing under contrasting climatic conditions. Certain ecological determinants governing the development of this lichen species have been revealed.

LARGE-SCALE PATTERNS OF DIVERSIFICATION IN THE WIDESPREAD LEGUME GENUS SENNA AND THE EVOLUTIONARY ROLE OF EXTRAFLORAL NECTARIES

Unraveling the diversification history of old, species-rich and widespread clades is difficult because of extinction, undersampling, and taxonomic uncertainty. In the context of these challenges, we investigated the timing and mode of lineage diversification in Senna (Leguminosae) to gain insights into the evolutionary role of extrafloral nectaries (EFNs). EFNs secrete nectar, attracting ants and forming ecologically important ant-plant mutualisms. In Senna, EFNs characterize one large clade (EFN clade), including 80% of its 350 species. Taxonomic accounts make Senna the largest caesalpinioid genus, but quantitative comparisons to other taxa require inferences about rates. Molecular dating analyses suggest that Senna originated in the early Eocene, and its major lineages appeared during early/mid Eocene to early Oligocene. EFNs evolved in the late Eocene, after the main radiation of ants. The EFN clade diversified faster, becoming significantly more species-rich than non-EFN clades. The shift in diversification rates associated with EFN evolution supports the hypothesis that EFNs represent a (relatively old) key innovation in Senna. EFNs may have promoted the colonization of new habitats appearing with the early uplift of the Andes. This would explain the distinctive geographic concentration of the EFN clade in South America.

Trade‐offs and habitat constraints in the establishment of epiphytic bryophytes

Summary 1. Diversity of patch‐tracking epiphyte metacommunities depends on successful colonization of new habitats. Habitat constraints and critical stages in the establishment have gained little attention in metacommunity studies, but a trade‐off between dispersal ability and establishment rate is often assumed. This assumption remains largely untested, and alternative dispersal and reproductive strategies offer several trade‐offs to be explored. 2. We used in vitro experiments to identify critical stages in the establishment of obligate epiphytic bryophytes with contrasting dispersal strategies [sexual via small (<20 μm) or large (>20 μm) spores, asexual via gemmae or gemmae‐like branchlets], and to identify habitat constraints of diaspore establishment and trade‐offs among species traits. 3. Across all stages of the establishment process, large asexual diaspores performed better than small sexual ones. Asexual species also had a higher ability to establish from fragments than sexual species. Germination of all diaspore types was limited by pH with highest germination rates at intermediate pH. Large moss spores showed a higher desiccation tolerance than small ones, but lower germination and protonemal growth rates. Liverwort spores had the lowest desiccation tolerance, germination and protonemal growth rates, but rapidly developed gametophytic shoots once they had germinated. 4. Combining the results with earlier studies on dispersal distances in epiphytes, our study demonstrated a trade‐off between dispersal distance and establishment ability, which may be central for the evolution of asexual dispersal in epiphytes. The evolution of spore size may additionally involve trade‐offs between high germination and protonemal growth rates, desiccation tolerance, and a rapid development from protonema to shoots. We suggest that trade‐offs in epiphytes are shaped by conflicting selection pressures imposed by habitat patchiness, landscape dynamics and irregular water supply.

Selection on breeding date and body size in colonizing coho salmon, Oncorhynchus kisutch

Selection during the colonization of new habitat is critical to the process of local adaptation, but has rarely been studied. We measured the form, direction, and strength of selection on body size and date of arrival to the breeding grounds over the first three cohorts (2003-2005) of a coho salmon (Oncorhynchus kisutch) population colonizing 33 km of habitat made accessible by modification of Landsburg Diversion Dam, on the Cedar River, Washington, USA. Salmon were sampled as they bypassed the dam, parentage was assigned based on genotypes from 10 microsatellite loci, and standardized selection gradients were calculated using the number of returning adult offspring as the fitness metric. Larger fish in both sexes produced more adult offspring, and the magnitude of the effect increased in subsequent years for males, suggesting that low densities attenuated traditional size-biased intrasexual competition. For both sexes, directional selection favoured early breeders in 2003, but stabilizing selection on breeding date was observed in 2004 and 2005. Adults that arrived, and presumably bred, early produced stream-rearing juvenile offspring that were larger at a common date than offspring from later parents, providing a possible mechanism linking breeding date to offspring viability. Comparison to studies employing similar methodology indicated selection during colonization was strong, particularly with respect to reproductive timing. Finally, female mean reproductive success exceeded that needed for replacement in all years so the population expanded in the first generation, demonstrating that salmon can proficiently exploit vacant habitat.

Seasonal variation in the nutritional vulnerability of first-stage larval porcelain crab, Petrolisthes laevigatus (Anomura: Porcellanidae) in southern Chile

In temperate marine environments, meroplanktonic larvae face seasonal variations in temperature and food availability. In a laboratory study conducted under seasonally varying temperature conditions, we evaluated the nutritional vulnerability in different cohorts (August, September, October, November, December, and January) of first-stage larvae of a porcellanid crab, Petrolisthes laevigatus. Besides continuously fed and starved control groups (FC, SC), the experimental treatments comprised: (1) differential periods of initial starvation and subsequent feeding (point-of-no-return, PNR: minimum time of initial starvation preventing recovery after later feeding); (2) initial feeding and subsequent starvation (point-of-reserve-saturation, PRS: minimum time of initial feeding allowing for food-independent development through the rest of the moulting cycle); (3) limited daily access to prey (feeding pulses, 4 and 6 h/day). The development time of FC larvae ranged from 10.6 ± 0.4 days (January) to 21.9 ± 2.6 days (August), without significant variation in mortality among cohorts. Under continuous absence of food (SC), first-stage larvae never survived to the zoea II. Short-term feeding pulses had significantly different effects on development time of different cohorts, but not on survival. The PNR was lowest in larvae produced near the end of spring (November). However, when the PNR was expressed as a percentage of the development time in FC larvae, no significant differences were found among cohorts (relative PNR: 32.8–42.5%). The relative PRS was reached after 60.6–73.5% of the development time in FC larvae. In spite of strong seasonal (presumably temperature-induced) differences in the absolute PNR and PRS values of different cohorts, the relative values were generally similar. This suggests that successive cohorts of early larvae can develop with similar success, unless severe winter conditions or oceanographic fluctuations cause a significant decline in short-term prey availability or plankton productivity. Due to long development duration at low temperatures, the larvae produced in winter and early spring have greater potential for dispersal, favoring a genetic exchange between distant populations and colonization of new habitats. Summer larvae, by contrast, may be more important for maintaining local populations. An index of nutritional vulnerability (NVI = PRS 50/PNR 50) is proposed in this paper to compare larvae with differential developmental times. In most larvae studied so far, the NVI is < 1, indicating some degree of independence of food. In larvae of P. laevigatus an index > 1 reflects a relatively high degree of dependence on planktonic food, especially in winter larvae.

Predators shape distribution and promote diversification of morphological defenses in Leucorrhinia, Odonata

Predators strongly influence species assemblages and shape morphological defenses of prey. Interestingly, adaptations that constitute effective defenses against one type of predator may render the prey susceptible to other types of predators. Hence, prey may evolve different strategies to escape predation, which may facilitate adaptive radiation of prey organisms. Larvae of different species in the dragonfly genus Leucorrhinia have various morphological defenses. We studied the distribution of these larvae in relation to the presence of predatory fish. In addition, we examined the variation in morphological defenses within species with respect to the occurrence of fish. We found that well-defended species, those with more and longer spines, were more closely associated with habitats inhabited by predatory fish and that species with weakly developed morphological defenses were more abundant in habitats without fish. The species predominantly connected to lakes with or without fish, respectively, were not restricted to a single clade in the phylogeny of the genus. Our data is suggestive of phenotypic plasticity in morphological defense in three of the studied species since these species showed longer spines in lakes with fish. We suggest that adaptive phenotypic plasticity may have broadened the range of habitats accessible to Leucorrhinia. It may have facilitated colonization of new habitats with different types of predators, and ultimately, speciation through adaptive radiation.

Evaluating Amphibian Declines with Site Revisits and Occupancy Models: Status of Montane Anurans in the Pacific Northwest USA

Amphibian declines have been reported in mountainous areas around the western USA. Few data quantify the extent of population losses in the Pacific Northwest, a region in which amphibian declines have received much attention. From 2001–2004, we resurveyed historical breeding sites of two species of conservation concern, the Western Toad (Bufo [=Anaxyrus] boreas) and Cascades Frog (Rana cascadae). We detected B. boreas breeding at 75.9% and R. cascadae breeding at 66.6% of historical sites. When we analyzed the data using occupancy models that accounted for detection probability, we estimated the current use of historically occupied sites in our study area was 84.9% (SE = 4.9) for B. boreas and 72.4% (SE = 6.6) for R. cascadae. Our ability to detect B. boreas at sites where they were present was lower in the first year of surveys (a low snowpack year) and higher at sites with introduced fish. Our ability to detect R. cascadae was lower at sites with fish. The probability that B. boreas still uses a historical site for breeding was related to the easting of the site (+) and the age of record (-). None of the variables we analyzed was strongly related to R. cascadae occupancy. Both species had increased odds of occupancy with higher latitude, but model support for this variable was modest. Our analysis suggests that while local losses are possible, these two amphibians have not experienced recent, broad population losses in the Oregon Cascades. Historical site revisitation studies such as ours cannot distinguish between population losses and site switching, and do not account for colonization of new habitats, so our analysis may overestimate declines in occupancy within our study area.

Dispersal by terrestrial stages of stream insects in urban watersheds: a synthesis of current knowledge

AbstractAdult dispersal and completion of life cycles by aquatic insects are essential for the persistence of populations, colonization of new habitats, and maintenance of genetic diversity. However, life-cycle stages and processes associated with the terrestrial environment often are overlooked when the effect of watershed urbanization on the persistence of insects associated with streams is examined. We reviewed and synthesized current literature on the known effects of watershed urbanization on the terrestrial stage of stream insects. Some research has directly examined the effects of watershed urbanization on dispersal, but much of the evidence we present is indirect and from related studies on aquatic insect life-history traits and dispersal abilities in nonurban watersheds. Our goal is to provide examples of potential impacts that warrant further study, rather than to provide a comprehensive review of all life-history studies. We discuss how watershed land use, riparian condition, and habitat qualit...

Presidential Address: Parasites on a Shrinking Planet

Planet Earth is shrinking at an ever-accelerating pace. It is not shrinking geologically, of course, or even atmospherically, unless you refer to the growing ozone hole. It is not even shrinking biologically in terms of net biomass, though some might argue that biodiversity is shrinking. But for Homo sapiens as a species, the planet is definitely shrinking. Why is this? Because, at least for now and the foreseeable future, planet Earth is our sole living space. The effective size of the available living space for any species is determined by the ability of that species to disperse throughout potential habitats, to successfully colonize those habitats, and to effectively utilize the resources available to them in those habitats. In terms of terrestrial habitats, since we are essentially a terrestrial species, we have pretty much dispersed to and colonized the entire planet. But we are an ingenious species, highly adaptable, and thus likely to find even other Earthly habitats to colonize under the ocean, beneath the earth's surface, in areas such as Antarctica and desert landscapes where we can trade minerals, wind and geothermal energy, and other non-biological resources for food. Homo sapiens seem to be the ultimate invasive species. But, are we really? At first glance, no other species, throughout any of Earth's history, seems to come close to rivaling the capacity of Homo sapiens for dispersal and colonization of new habitats. The exceptions, of course, are the other species that we intentionally, or unintentionally, take with us as we disperse. These include the plants, animals, and microbes that we take with us as sources of food and fiber the livestock, the fish, the poultry, and so on. Also included are the parasites those that live on and in us, those that live on and in the species that we move around with us, and especially those that use both we and our food animals and companion animals as hosts. Since there are apparently more parasitic organisms than free living, these parasites must be actually the ultimate invasive species, using their lowly human and synanthropic animal hosts as vehicles for their own dispersal. Except for the pets or companion animals, we don't really want to take the other species with us. But we have no choice we have to eat. And we certainly don't want to take the parasites with us. But we seem to have no choice here either the parasites are just too adaptable, too ingenious, too good at staying with us despite our greatest efforts to leave them behind.

Patterns of house infestation dynamics by non-domiciliatedTriatoma dimidiatareveal a spatial gradient of infestation in rural villages and potential insect manipulation byTrypanosoma cruzi

Chagas disease is a major vector-borne parasitic disease in Latin America, primarily transmitted to humans by triatomine vectors. Non-domiciliated triatomine species such as Triatoma dimidiata in the Yucatan peninsula, Mexico, can transiently invade houses and are emerging as a major challenge to control Trypanosoma cruzi transmission to humans. We analyzed the spatio-temporal spreading of house infestation by T. dimidiata in four rural villages. Triatomines were collected in four rural villages over a 2 years period, and the spatio-temporal patterns of infestation were analyzed. Triatomines were consistently more abundant at the periphery of villages than in centers, indicating a much higher risk of T. cruzi transmission at the periphery. Male T. dimidiata were found further in the center of the village, while females remained closer to the periphery, suggesting differential dispersal capabilities between sexes, although the timing of dispersal appeared identical. Surprisingly, infected females were consistently collected in houses much further from the surrounding bushes than non-infected females, while the distribution of males was unaffected by their T. cruzi infection status, suggesting an increased dispersal capability in infected females. The spatial structure of infestation should be taken into account for the prioritization of vector control activities within villages, and spatially targeted interventions may be explored. A potential vector manipulation by T. cruzi, observed for the first time in triatomines, may favor parasite transmission to new hosts.

Reassessing the importance of granivorous pigeons as massive, long-distance seed dispersers

Long-distance dispersal (LDD) of plants remains as a little-understood, key ecological process. We present evidence indicating that granivorous pigeons may disperse large amounts of viable seeds when they die with seeds in their crops at long distance from the parent plant. Research was conducted in Eared Dove (Zenaida auriculata) breeding colonies in central Argentina where breeding populations may reach over 8000 doves/ha. We measured (a) crop seed viability and germination rate from dead doves and (b) daily travel distance from the breeding colonies to the feeding grounds. Seed viability was over 50% in fresh adult and nestling samples. Seed-germination rate ranged between 35% and 65%, even in corpses left on the ground for 30 days. Maximum doves' daily flight distance from the breeding colonies was 117 km. The estimated annual seed deposition per hectare resulting from crop spillage in two breeding colonies was 10.95 and 9.66 Mg, respectively. Significant ecological implications of dove-crop spillage include seed dispersal among fragments, rapid colonization of new habitats including islands, and dispersal of large volumes of weed and transgenic material. A preliminary assessment of dispersal kernel generated by crop spillage in colonial Eared Doves is included.

Influence of Landscape Elements in Riparian Buffers on the Conservation of Semiaquatic Amphibians

Studies on riparian buffers have usually focused on the amount of land needed as habitat for the terrestrial life stages of semiaquatic species. Nevertheless, the landscape surrounding wetlands is also important for other key processes, such as dispersal and the dynamics of metapopulations. Multiple elements that influence these processes should therefore be considered in the delineation of buffers. We analyzed landscape elements (forest cover, density of roads, and hydrographic network) in concentric buffers to evaluate the scale at which they influence stream amphibians in 77 distinct landscapes. To evaluate whether our results could be generalized to other contexts, we determined whether they were consistent across the study areas. Amphibians required buffers of 100-400 m of suitable terrestrial habitat, but interspecific differences in the amount of habitat were large. The presence of amphibians was related to roads and the hydrographic network at larger spatial scales (300-1500 m), which suggests that wider buffers are needed with these elements. This pattern probably arose because these elements influence dispersal and metapopulation persistence, processes that occur at large spatial scales. Furthermore, in some cases, analyses performed on different sets of landscapes provided different results, which suggests caution should be used when conservation recommendations are applied to disparate areas. Establishment of riparian buffers should not be focused only on riparian habitat, but should take a landscape perspective because semiaquatic species use multiple elements for different functions. This approach can be complex because different landscape elements require different spatial extents. Nevertheless, a shift of attention toward the management of different elements at multiple spatial scales is necessary for the long-term persistence of populations.

Distribution, Population Structure and Habitat Use of the Endangered Saint Francis Satyr Butterfly, Neonympha Mitchellii Francisci

The endangered St. Francis Satyr (Neonympha mitchellii francisci) is a small sedentary butterfly and one of the rarest in North America. Our study examined various quantitative aspects of this butterfly's biology, including the distributional range, habitat associations, population size and trends, demographic parameters and spatial aspects of population structure. The range of N.m. francisci distribution is restricted to DoD lands at Ft. Bragg, North Carolina, where the butterfly utilizes wetland habitats, predominantly those that have previously been impounded by beaver. In situ habitat associations and captive rearing experiments indicate that multiple sedges in the genus Carex, particularly C. mitchelliana, may be important larval food plants. Subpopulation estimates range between 49–739 individuals at any one site, while cumulative population estimates range between 700–1400 individuals for all accessible areas on Ft. Bragg. Habitats occupied by N.m. francisci are frequently subject to burning or flooding and thus butterfly subpopulations are extremely dynamic, fluctuating in response to these disturbances. This regular disturbance regime dictates that dispersal is necessary for population persistence. Several inter-colony movements were measured during capture-recapture studies and we observed both subpopulation extinctions and colonization of new habitat through the period of our studies. Conservation of N.m. francisci depends on accommodating unique aspects of its populations, including its dependence on beaver and its multi-tiered metapopulation structure.

Diel Flight Pattern and Flight Performance of Cactoblastis cactorum (Lepidoptera: Pyralidae) Measured on a Flight Mill: Influence of Age, Gender, Mating Status, and Body Size

Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) is an invasive herbivore that poses a serious risk to Opuntia cacti in North America. Knowledge of the flight behavior of the cactus moth is crucial for a better understanding of natural dispersal, and for both monitoring and control. We used computer-linked flight mills to investigate diel flight activity and flight performance in relation to gender, age, mating status, and body size. Maximal flight activity for both mated and unmated moths occurred during twilight, whereas flight activity was low during photophase. The total distance flown and the number of initiated flights within a diel cycle were higher in both unmated and mated females than in males, but the longest single flight was similar in both genders. These findings suggest that pheromone trap captures of males likely indicate the simultaneous presence of females and that mated females might even be in areas where males are not detected yet. Flight performance heterogeneity was large, with a small portion of the population (both males and females) performing long unbroken flights, whereas the majority made short flights. Females had higher pupal and adult body size and shorter longevity than males. A few individuals, particularly young mated females, flying long distances may be important for active spread of a population and the colonization of new habitats. Implications of this study in the control of the cactus moth by using the sterile insect technique are discussed.