Ecotone Habitats Research Articles

Forest bird diversity and ski-runs: a case of negative edge effect

Among tourist activities in the Alps, winter sports have a prominent role because of the large scale of changes they cause at the habitat and landscape level. We have analysed whether ski resorts lead to significant threats to the avian diversity in the coniferous forests of the western Italian Alps, by comparing the bird communities of plots located in (1) the forest interior, (2) forest at the edge of ski-runs and (3) forest at the edge of pastures (the latter two are anthropogenic elements of forest fragmentation). Ski-runs produce a negative edge effect in the study forests: plots at their edges present lower bird species richness and Shannon diversity than those located in the forest interior or at the edges of pastures. In particular, birds typical of ecotone habitats seem to favour forest plots set at the edge of pastures. Ski-run-edges are linear landscape features that create high contrast edges; conversely, vegetation structure is more complex at the edge of pastures, attracting a rich and diverse avifauna. In the study area, pastures tend to be abandoned whereas winter sport resorts are increasing in extent. Accordingly, there is a need for coordinated management and cooperation between sport- and land-management agencies, in order to preserve native biodiversity while simultaneously managing land for sport activities.

Blood Parasites of Some West African Rainforest Birds

A total of 969 birds representing 121 species of 21 families from the West African nations of Cameroon, Equatorial Guinea and Ivory Coast were examined for haematozoa using thin blood smears; 277 individuals (28.6%) harbored blood parasites. The parasites identified included species of Haemoproteus (7.7% prevalence), Plasmodium (10.7%), Leucocytozoon (4.6%), and Trypanosoma (7.3%). In addition, microfilariae of filariid nematodes were present in 3.6% of the individuals examined. The birds were collected over a period of 12 years, from 1989-2001, from rainforest and ecotone habitats. We report a relatively high prevalence of parasites in colonial nesting birds, and two species of ground nesting birds. In addition, we compared data from bird species collected at a site identical to a previously published study, and did not find significant differences in parasite prevalence between the two years constituting two different seasons. Our results are also compared to other studies in Africa that implement similar and different methodologies.

Lizard community structure across a grassland – creosote bush ecotone in the Chihuahuan Desert

I investigated the distribution and abundance of lizard species (Aspidoscelis inornatus, Aspidoscelis tesselatus, Aspidoscelis tigris, Aspidoscelis uniparens, Cophosaurus texanus, Crotaphytus collaris, Eumeces obsoletus, Gambelia wislizenii, Holbrookia maculata, Phrynosoma cornutum, Sceloporus magister, and Uta stansburiana) across a desert grassland – creosote bush (Larrea tridentata) ecotone in Dona Ana County, New Mexico. The ecotonal area in the Jornada del Muerto basin has increased dramatically in the past 150 years because of the rapid spread of creosote bush. I asked four related questions: how large and where is the ecotone based on vegetative structure, and do lizard abundance and diversity change across the ecotone? Vegetation data were analyzed using discriminate function analysis to determine the extent of the ecotone. Changes in lizard abundance across the ecotone were analyzed by analysis of variance. During two summers, 677 individual lizards of 9 genera and 12 species were captured. Lizard abundance increased with increasing distance from the ecotone and was similar in grassland and creosote bush habitat. Grasslands had higher species richness than both the creosote bush and ecotone habitats. Grassland sites had greater habitat heterogeneity than did creosote bush sites. No ecotone specialist species were detected, and all common lizard species could be found in each habitat. Three potential explanations for decreased abundance in the ecotone are presented: (1) increased risk of predation, (2) decreased prey abundance, and (3) lack of species-specific microhabitat requisites.

A Perplexing Outbreak of Mice in Patagonia, Argentina

Early in spring, 1997, remarkably large numbers of mice appeared in the dense forests near the western end of Lago Nahuel Huapi, Argentina. Dead mice that washed up on nearby beaches at this time were fat, had full stomachs and were young or young-adults born unusually late in the preceding autumn and winter. These mice represented an aperiodic outbreak that extended over 300 km along the Andes. By analysis of trapped samples, the demographics of the two main species in this outbreak (Oligoryzomys longicaudatus and Abrothrix longipilis) were compared with demographics of the same species during the preceding 21 years. In spring of 1997, trap success for O. longicaudatus in areas of the outbreak was as high as 46%; for A. longipilis it was 22%. Neither males nor females of either species entered breeding condition in 1997 during the usual season of reproduction in spring, nor in the following summer, leading to the collapse of the populations. Numbers of Oligoryzomys decreased steadily to 15% in autumn and a normal 2% in the following spring, at which time reproduction resumed. The 1997 springtime populations in adjacent ecotone and steppe habitats to the east had not increased, contained no young individuals, and overwinter individuals reproduced normally. During the breeding season, O. longicaudatus in these populations increased more rapidly than did A. longipilis, and during the winter, they decreased faster. The unusual winter reproduction preceding the outbreak may have resulted from an increase in some deep-forest food source that in turn was responding to two successive, unusually warm winters. Predation played a negligible role in the population collapse. The mouse outbreak was not accompanied by an increase in human cases of hanta pulmonary syndrome, a disease for which O. longicaudatus is a reservoir.

Seasonal activity and spatial distribution of host-seeking adults of the tick Dermacentor variabilis.

The seasonal temporal and spatial distribution and emergence of overwintering and summer cohorts of host-seeking American dog tick, Dermacentor variabilis (Say) (Acari: Ixodidae), adults were examined for 5 years in the Bluegrass region of Kentucky. Weekly drag cloth sampling was conducted from early March until late September 1992-1995 and early March until the end of May 1996. Overwintering adult cohorts became active in early to mid-April followed by bimodal host-seeking activity each year, with the duration and intensity of the first activity period being related to the previous year's summer cohort activity. The first activity peak extended from mid-April through late May and the second activity peak occurred in July. All host-seeking activity ceased by early August, except in 1995, when activity ended on 22 August. Laboratory survival of adults, collected weekly during 1993-1996, was used to estimate the emergence of summer adult cohorts. Summer adult cohorts became active in late May or early June and overlapped with overwintering adult host-seeking activity. The termination of host-seeking activity in overwintering adults could not be determined using the methods employed in this study and is most likely to have continued for the entire season. Host-seeking adults displayed contagious distribution patterns along trails bordering ecotone habitats, as determined by fitting a negative binomial frequency distribution to weekly sampling data. These patterns did not vary from year to year. In addition, the location of D. variabilis activity did not change from year to year, which suggests that microhabitats within apparently homogeneous environments enhance adult survival and lead to 'hot spots' of tick activity despite the ability of vertebrate hosts to disperse D. variabilis populations more widely. These data better define our understanding of D. variabilis adult seasonal and spatial host-seeking activity, estimate for the first time the intensity of summer cohort host-seeking activity, and relate summer cohort activity with spring activity the following year.

Quatermalacological analyses for modeling of the Upper Weichselian palaeoenvironmental changes in the Carpathian Basin

The Late Pleistocene environmental history of the Carpathian Basin can be regarded as one of the missing links to our understanding of the last glacial development of Europe. Changes in the radiocarbon-dated Mollusc faunas of the loess areas, along with the palaeogeographic interpretations implied by them seem to underlie the latest results gained from radiocarbon dated pollen analysis of the region. Changes in the Mollusc fauna refer to nine short-lived (1000–3000 years) cyclical palaeoclimatological alterations, which repeatedly transformed the palaeoecological conditions and vegetation in the Carpathian Basin between 34 and 12 kyr. On the basis of malacological data the presence of a major palaeoclimatic trend could be assumed for periods of both warming and cooling in the Carpathian Basin. The mildest July palaeotemperatures were recorded in the SW parts, and the coldest ones were recorded in the NE parts of the basin. Humidity and vegetation cover displayed a large-scale mosaic type heterogeneity reflecting the modifying effect of local factors. It seem that the Upper Weichselian environment was mosaic or mosaic-like in the Carpathian Basin, and the different plants and animals spread from different ecological spots during periods of climate change when the distribution of the forest, grassland, ecotone, or tundra-like habitats changed.

A comparison between mice and rats as sentinels for Leptotrombidum imphalum (acari: trombiculidae) in northern thailand

A five day study was conducted in northern Thailand to determine the suitability of Rattus rattus (L.) and Mus musculus (L.) as sentinel animals for larval Leptotrombidium imphalum Vercammen-Grandjean & Langston (also known as chiggers) in ecotonal and plantation habitats. Chiggers infested sentinel rats with a significantly higher prevalence and mean intensity than sentinel mice (P<0.05). There were no significant differences in prevalence or mean intensity of L. imphalum infesting rats in ecotones or the plantation.

A transect through a clastic-swamp to peat-swamp ecotone in the Springfield Coal, Middle Pennsylvanian age of Indiana, USA

Permineralized fossil plants in coal balls were collected along a kilometer transect through an organic-rich shale in the Springfield Coal in southwestern Indiana. The organic shale is an upper bench of the Springfield Coal in an area where the coal is split into an upper and lower bench by a complex system of clastics that originated as a splay. The clastic wedge, described as the Folsomville Member/Leslie Cemetery paleochannel, is up to 6 km wide and 15 m thick. The transect begins approximately 100 m from the edge of the clastic wedge that splits the coal seam and follows the upper bench of coal over and toward the center of the clastic wedge. The dominant elements of the vegetation were the lycopsid tree Paralycopodites brevifolius and several species of medullosan pteridosperms. This report confirms the ecotonal habitats of this vegetation.

A Role for Ecotones in Generating Rainforest Biodiversity

Gene flow and morphological divergence were measured among 12 populations of a common species of rainforest passerine. Populations in the forest and the ecotone (the transition zone between the African rainforest and savanna) are morphologically divergent, despite high gene flow, and morphological differences between habitats are as large as those found between related species. In contrast to past theories of rainforest speciation, which emphasize geographic isolation, these results suggest that natural selection may play an important role in generating rainforest biodiversity. Because ecotone habitats may be a source of evolutionary novelty, greater attention should be paid to their conservation in order to preserve the processes that may be important to maintain rainforest diversity.

Influence of Season and Habitat on Ixodes scapularis Infestation on White-Footed Mice in Northwestern Illinois

The effects of season and habitat on the infestation of the white-footed mouse (Peromyscus leucopus) by immature Ixodes scapularis were studied at Castle Rock State Park, northwestern Illinois, during June-October 1991. Relative density of larvae on mice was higher in mid-late summer (13.7 ticks per mouse) than during the rest of the study period, whereas prevalence of nymphal infestation was highest in early summer (33.3%). Relative density of I. scapularis larvae and prevalence of nymphs on mice did not differ significantly among bottomland forest, field-forest ecotone, and upland forest habitats. In bottomland forest, total number of ticks collected from mice (472 larvae and 13 nymphs) and P. leucopus population density (6.6 mice per 0.36 ha) were higher than in the other habitats. Temporal patterns of numbers of larvae collected from mice and through dragging in bottomland forest were significantly correlated.

Alteration of patch boundaries on the floodplain of the regulated river trent, UK

AbstractInvestigations were carried out into the contemporary distribution and structure of the vegetation communities at Gunthorpe, Nottinghamshire on the floodplain of the River Trent. A 60 km reach of the river was examined to determine the overall distribution and structure of vegetation communities; the Gunthorpe site was chosen as a representative example. Three hundred and thirty‐nine separate plots were examined and the site contained 132 species. It is clear that the extent of zones of discontinuity or transition (ecotones) between different vegetation patches has decreased due to long‐term land‐use management. The overall number of vegetation patches has also been reduced. A hierarchy relating boundaries to external influences is proposed and the relationship of ecotones to more clearly differentiated patch habitats identified. Highest species diversity is seen to be associated with the transition zones or ecotonal habitats, particularly under conditions of moderate disturbance intensity. It is concluded that the ecotones remaining still provide a habitat for a wide range of species with differing autecological requirements, but all typical of less disturbed alluvial meadows and marshes. These zones of transition potentially provide a pool for species expansion given improved ecological conditions following river restoration measures.

Ixodes dammini (Acari: Ixodidae) infestation on medium-sized mammals and blue jays in northwestern Illinois.

High prevalence of infestation of five species of medium-sized mammals and blue jays, Cyanocitta cristata (L.), by immature Ixodes dammini Spielman, Clifford, Piesman and Corwin was found in Castle Rock State Park in northwestern Illinois during May-August 1991. Raccoons, Procyon lotor L., and opossums, Didelphis virginiana Kerr, were infested with the highest larval densities and were trapped primarily in bottomland forest and ecotone habitats. All species had similar nymphal densities, except the eastern cottontails, Sylvilagus floridanus Allen, which were infested with fewer nymphs. Infestation by I. dammini is reported for the first time for fox squirrels, Sciurus niger E. G. St. Hilaire, and for the first time in the midwestern United States for blue jays, C. cristata. These two species were hosts for nymphs in upland forest habitat. Molting rates varied among ticks that fed on different host species and among larvae that fed on individuals of the same species. Molting rate is proposed as an important factor in determining the relative importance of a host species to I. dammini population dynamics.

Role of the eastern chipmunk as a host for immature Ixodes dammini (Acari: Ixodidae) in northwestern Illinois.

Infestation of the eastern chipmunk, Tamias striatus L., by immature Ixodes dammini Spielman, Clifford, Piesman and Corwin was studied in Castle Rock State Park in northwestern Illinois during June-October 1991. Mean larval density peaked in August, while nymphal density declined steadily through the study period. Prevalence of tick infestation was high throughout the trapping period. Tick distribution on chipmunks was aggregated in most of the sampling periods. Levels of I. dammini infestation recorded on chipmunks in this survey are higher than previous results recorded in the northeastern and midwestern United States. Chipmunks had significantly higher levels of nymphal I. dammini infestation than white-footed mice (Peromyscus leucopus Rafinesque). A major role of the eastern chipmunk as a host for immature I. dammini in upland forest habitat in northwestern Illinois can be established. In bottomland and ecotone habitats where chipmunks were scarce, P. leucopus contributed most to the feeding of larval ticks.

Can Parthenogenetic Cnemidophorus laredoensis (Teiidae) Coexist with Its Bisexual Congeners?

-Wright and Lowe (1968) and Cuellar (1977) suggested that parthenogenetic Cnemidophorus can survive only in isolation from their bisexual congeners because the latter would otherwise eliminate the parthenoforms through competition and/or hybridization. Data from studies of the parthenogenetic clone LAR-A of the Cnemidophorus laredoensis subgroup suggest this hypothesis is not correct. The bisexual species C. gularis occurs at 24 of the 39 sites at which LAR-A has been found, and neither form is consistently more abundant than the other at syntopic sites. The literature documents many cases where parthenogenetic whiptails coexist with their bisexual congeners, suggesting parthenoforms do not require isolation as previously believed. One of two things must be happening to allow parthenoforms to coexist with bisexuals: (1) competition and do not occur; or (2) these processes do occur but some other factor counteracts their effect. At present, too little data exist to evaluate which of these alternatives is correct. However, analysis of lizard diets at three sites of syntopy and data reported in studies of other parthenoforms are used to advance testable hypotheses in the hope of stimulating future research. The lizard genus Cnemidophorus (Teiidae) includes several forms that reproduce by true parthenogenesis in addition to many bisexual species. The parthenoforms originate as hybrids between bisexual species; the hybrids then reproduce asexually to generate clones of genetically identical individuals (Wright, 1978; Cole, 1979). The existence of parthenoforms presents biologists with an interesting evolutionary problem: how do such forms persist in a world dominated by sexually reproducing species that are presumably better adapted to the environment through natural selection? In their classic paper, Wright and Lowe (1968) proposed the weed hypothesis, which states that parthenogenetic whiptails can become established only in disturbed, marginal, or ecotonal habitats because such habitats are unsuitable for bisexual whiptails. A slightly different view was proposed by Cuellar (1977) who suggested parthenogenetic whiptails occupy only floodplain, beach, or lakeside habitats because parthenoforms can rapidly colonize areas where natural disasters periodically eliminate lizard populations, and because bisexual species are usually absent from such habitats. The implication of both hypotheses is that parthenoforms are poor competitors, presumably because their limited genotypic diversity translates into narrow ecological breadth (Bell, 1982; Case and Taper, 1986). Therefore parthenoforms can avoid competitive exclusion by their bisexual congeners only by occupying disturbed habitats. Cuellar (1977) also emphasized that isolation from bisexual forms ensures that a parthenoform will not lose its genetic identity through hybridization, a phenomenon termed destabilizing hybridization by Lynch (1984). This occurs if diploid parthenoforms mate with males of bisexual species to produce triploid hybrids that are either sterile or are parthenogenetic themselves (Lynch, 1984; Vrijenhoek, 1989). The latter case should lead to the replacement of diploid parthenoforms by triploid parthenoforms. Hybridization with bisexual species might also be detrimental to a parthenoform if the fertilization of a parthenogenetic egg caused the egg to fail to develop, resulting in waste of reproductive effort (White and Contreras, 1979). Both Wright and Lowe (1968) and Cuellar (1977) suggested that parthenoforms should rarely be found at site where bisexual species occur, and in those ra e instances where the two forms do co-occur, the bisexual species should be rare enough that it does not exert a strong impact on the parthenoform. However, these hypotheses have not been tested rigorously. The parthenogenetic Cnemidophorus laredoensis subgroup comprises several allodiploid clones that occupy a narrow zone on either side of the Rio Grande from Del Rio (Val Verde County), Texas, to within 16 km of the Gulf of Mexico (Walker, 1987a, b). The subject of this paper is the clone LAR-A, (originally described as Cnemidophorus laredoensis by McKinney et al., 1973). A second major clone, named LAR-B, discovThis content downloaded from 207.46.13.160 on Mon, 17 Oct 2016 05:18:30 UTC All use subject to http://about.jstor.org/terms M. A. PAULISSEN ET AL. TABLE 1. Snout-vent lengths (SVL) and mass of LAR-A and C. gularis at three sites in Texas. Values are mean + standard deviation, sample sizes are given in parentheses. Statistically significant differences, as evaluated by Mann-Whitney U tests, are indicated by an asterisk. The sample sizes for SVL and mass at Garceno differ because lizards were not weighed during the 1 May collection.

Reciprocal Allogrooming in Dam‐reared and Hand‐reared Impala Fawns

AbstractAmong adult females and males of African antelope impala are unique in their performance of reciprocal allogrooming. The occurrence of this behaviour in neonatal impala fawns was explored in a free‐ranging impala herd at the San Diego Wild Animal Park where 5 dam‐reared fawns were observed from birth through 10 weeks of age. One‐way maternal grooming and reciprocal allogrooming with the dam and non dam partners emerged as distinct behavioural systems. Maternal grooming, directed mostly to the anogenital area, was typical of that seen in other ungulates, and sharply declined over the first two weeks. Reciprocal allogrooming, characterized by alternate exchanges of grooming bouts with a partner in the same manner as in adults, was seen as early as 3–8 d after birth. All fawns were grooming with unrelated adult females by the end of the second week. By week 2 virtually every measure of reciprocal allogrooming by fawns (grooming delivered per hour, reciprocity, and percent of encounters initiated) was as high as for adults. The appearance of this reciprocal allogrooming pattern, especially at such an early age, appears to be unique among ungulates, and possibly mammals in general. Three hand‐reared impala fawns, deprived of the opportunity to interact with older herdmates, but having access to impala fawns and heterospecific fawns, were observed from 1–3 mo of age. The hand‐reared impala showed no alteration in the occurrence of reciprocal allogrooming behaviour compared with the dam‐reared control fawns, indicating that allogrooming experience with older animals was not required for the appearance of reciprocal allogrooming at an early age. Interestingly, hand‐reared fawns persisted in grooming heterospecific fawns despite the fact that heterospecifics rarely reciprocated grooming. We postulate that the strong predisposition for impala young to groom others may be related to the threat of tick infestation in the impala's ecotone habitat.

Late Quaternary Plants and Vertebrates from Picacho Peak, Arizona

Eighty-two plant and 26 small vertebrate taxa were identified from four radiocarbon dated woodrat (Neotoma sp.) midden samples from a rock crevice at 655 m elevation on Picacho Peak, Pinal Co., Arizona. A late Wisconsin (11,100 to 13,170 YBP) pinyon-juniper-oak woodland dominated by Pinus monophylla (singleleaf pinyon) and Juniperus cf. osteosperma (Utah juniper) and J. erythrocarpa/monosperma (redberry/oneseed juniper) shifted to a more xeric juniper-oak woodland/chaparral in the early Holocene (9,420 to 10,280 YBP). Extralocal species that no longer live on Picacho Peak were 29.9% in the late Wisconsin and 20.1% in the early Holocene with the greatest changes in longlived trees, shrubs, and succulents. The biogeographic and taxonomic significance of Scaphiopus hammondi (western spadefoot) and the ecological adaptability of Phrynosoma platyrhinos (desert horned lizard), Micranthe whitneyi (elf owl), and Neotoma cf. albigula (white-throated woodrat) are discussed. All taxa in the vertebrate fauna are widespread in desertscrub and desert-grassland, still occur in the area, and enter woodlands only at the upper or northern edges of their ranges. The typical inhabitation of woodlands by these vertebrates and anomalous associations in the flora probably reflect the expansion of equable climates that now characterize ecotonal habitats during the late Wisconsin glacial. Analyses of plant remains preserved in ancient woodrat (Neotoma sp.) middens are providing excellent developmental sequences for local floras and vegetation for the last 20,000 to 40,000 years on rocky slopes in the southwestern United States and northern Mexico (Van Devender et al., 1987a). During the last glacial (the Wisconsin) period, woodlands expanded into the modern Sonoran Desert in southwestern Arizona and adjacent California (111* to 113*W). Pinyon-juniper-oak woodland dominated by Pinus monophylla (singleleaf pinyon) was at 600 to 1,555 m elevation with a xeric Juniperus californica (California juniper) woodland down to about 300 m, and Larrea divaricata (creosotebush) desertscrub at lower elevations along the Colorado River and around the head of the Gulf of California in Sonora and Baja California (Van Devender, 1990). Animal remains are much less common than plants in woodrat middens but provide insight into faunal responses to changing climate and vegetation (Van Devender and Mead, 1978; Van Devender et al., 1979; Mead and Phillips, 1981; Mead et al., 1983). Here we report the pla and vertebrate remains in woodrat middens from Picacho Peak, Arizona. MATERIALS AND METHODS-Picacho Peak was an isolated butte in Picacho Peak State Park rising from 550 m elevation at the base to 1,030 m at the top (Briscoe, 1967; Shafiquallah et al., 1976; Yeend, 1976). The nearest mountains of larger size were the Santa Catalina Mountains just north of Tucson (55 km SE) that rose to 2,790 m elevation. The lowest elevation near Picacho Peak was 520 m along the Santa Cruz River (3 km SW). The local climate was characterized by infrequent winter freezes, hot summers, and biseasonal rainfall from Pacific winter frontal storms and the subtropical summer monsoon. Mean temperatures for Eloy (15 km NW) at 475 m were 10.8*C for January and 32.3*C for July with extremes of 10.6*C and 47.2*C (Sellers and Hill, 1974). Precipitation was 215 mm/year with 40.6% falling from June to September. Picacho Peak was in the relatively well-watered Arizona Upland Subdivision of the northeastern Sonoran Desert (Shreve, 1964; Turner and Brown, 1982). The vegetation on rocky slopes and bajadas was dominated by Cercidium microphyllum (foothill paloverde), Olneya tesota (ironwood), and Carnegiea gigantea (saguaro) in This content downloaded from 207.46.13.149 on Mon, 03 Oct 2016 06:10:19 UTC All use subject to http://about.jstor.org/terms September 1991 Van Devender et al.-Late Quaternary plants and vertebrates 303

Response of Cottontail Rabbit Populations to Herbicide and Fire Applications on Cross Timbers Rangeland

Knowledge of how resident wildlife populations respond to brush management strategies is especially limited for rangelands in the cross timbers vegetation type of Oklahoma. We examined how cottontail rabbit (Sylvilagus floridanus) density and habitat use were influenced by applications of tebuthiuron or triclopyr, with and without annual burning, on cross timbers rangeland. Line transect flush-counts, mark-recapture livetrapping, and fecal pellet counts were used to evaluate seasonal differences in population density among 5 brush control treatments. Cottontail rabbits (n = 225) were flushed along 362 km of line transects during 5 census periods. Density in winter was consistently lower than summer for all treatments, except for the untreated control in winter 1987. Line transect density estimates varied from 0 to 1.975 rabbits/ha and suggested that herbicide and annual burning treatments had a positive influence on cottontail rabbit populations compared to untreated controls. Mark-recapture density estimates did not differ among treatments. Fecal pellet counts were greater on herbicide-treated pastures than an untreated control in both spring and fall. Prairie-eastern redcedar (Juniperus virginiana L.) and forest-prairie ecotone habitats were utilized greater than expected by cottontail rabbits. Mature hardwood overstory and mixed-brush habitats were avoided. Tebuthiuron and triclopyr effectively deceased hardwood overstory and increased preferred habitats for cottontail rabbits.

Ecological and genetic separation of three sympatric species ofAedes(Diptera: Culicidae) from the Kenya coast

AbstractAedes ledgeriHuang,A. soleatusEdw. andA. calceatusEdw. of the group ofA. aegypti(L.) of the subgenusStegomyiacollected on the coast of Kenya are distinguished on the strength of ecological and genetic (isozyme) data. The preferred oviposition sites ofA. ledgeriandA. soleatuswere tree holes above ground level, whereasA. calceatusfavoured abandoned gastropod shells.A. ledgeriwas most abundant in ecotonal habitats andA. soleatusin undisturbed forest At least two diagnostic enzyme loci separated each of the three species pairs.

A GEOGRAPHICAL ANALYSIS OF QUANTITATIVE MORPHOLOGICAL VARIATION IN THE GRASSHOPPER ARPHIA CONSPERSA.

The speckled rangeland grasshopper, Arphia conspersa Scudder (Acrididae; Oedipodinae) ranges from Alaska and northern Canada to northern Mexico, and from California to the central Great Plains (Strohecker et al., 1968; Vickery, 1967; Helfer, 1953). Its altitudinal range is also quite wide, being from less than 1,000 m above sea level to nearly 4,000 m in the southern portion of the range (Alexander and Hilliard, 1969). Over this entire area the animal is springbrooded, the actual time of adult emergence being dependent on the onset of spring and final melt of winter snow. The distribution pattern of A. conspersa within this extensive geographic and topographic range is highly discontinuous, owing to its narrow habitat preferences and distinctive behavior patterns (Alexander and Hilliard, 1969; Willey and Willey, 1967, 1969,1971). Ecologically, the species is limited to shortgrass prairies and forest or brushland openings, areas in which the animal's primary food sources, narrow-leaved grasses, are found interspersed with numerous small spaces of bare ground which are necessary for the performance of courtship rituals. Hence, dense forest, tall grass meadows, and xeric scrubland are uninhabited by A. conspersa, while ecotonal habitats, such as roadside meadows and old logged areas, may be slowly colonized (Willey and Willey, 1971). Moderately grazed pastures can also support large populations. Within such a habitat structure, A. con-

Biology and Larval Feeding Habits of Three Species of Renocera (Diptera: Sciomyzidae) That Prey on Fingernail Clams (Mollusca: Sphaeriidae)1

Information is provided on the life cycles and larval feeding habits of 3 North American species of Renocera that prey on fingernail clams. Adults of R. brevis (Cresson) occur in open, permanently wet marshes; those of R. amanda Cresson are associated with vernal pools and seepage areas in deciduous woodlands; and those of R. longipes (Loew) usually are found in wet ecotone habitats between open marshland and lowland forests. Adults of R. amanda and R. brevis emerge in May, but R. longipes is temporally separated from the other 2 species by delaying its adult emergence time until mid-June. Renocera brevis has at least 2 generations/yr; whereas both R. amanda and R. longipes are univoltine. Larvae of all 3 species prey solely on fingernail clams of the molluscan family Sphaeriidae. Newly-hatched larvae leave the surface film and seek out small clams among bottom debris. They remain within the mantle cavity of their prey 4–8 days before killing it. Older larvae remain at the surface film of shallow pools and feed as overt predators, killing prey quickly and remaining with it for only a few hours. Individual larvae kill between 14 and 25 clams. Puparia are formed at the water's surface or in shoreline debris. Species of Renocera are among the 1st insects and the 1st Sciomyzidae known to attack members of the molluscan class Pelecypoda; nearly all other species of the family feed on members of the class Gastropoda. A key to the 5 Nearctic species of Renocera is presented.