Edge Of Woods Research Articles

Dispersal of Blacklegged Tick (Acari: Ixodidae) Nymphs and Adults at the Woods–Pasture Interface

Marked nymphal and adult blacklegged ticks, Ixodes scapularis Say, were released in 4 host-exclusion cages and 4 similar control areas, all straddling the woods-pasture interface. Both nymphs and adults were recaptured by flagging at regular intervals outside the cages, having therefore actively dispersed > 4.5 m (i.e., without involvement of vertebrates). Nymphs were recaptured much more often ( > 90%) in the woods than pastures, whereas 62.8% of recaptured adults were taken in pastures. Females were recaptured in equal numbers in pastures and woods, but 75.4% of recaptured males were in pastures. Adults that dispersed into pastures were recaptured an average of 1.6 and 3.7 m from the woods edge in 1992 and 1993, respectively, and as far as 7-8 m from the woods edge. Nymphs dispersed shorter distances than adults with 66% of the recaptured nymphs found 2-3 m from their release points, and > 46% of recaptured adults found > 5 m from their release points. Twice as many nymphs were recaptured from the caged than uncaged sites. The lower numbers of nymphs recaptured from control sites compared with caged sites are probably the result of host acquisition; the absence of this discrepancy with the adults may reflect by their ability to move relatively quickly from the host-exclusion cages and become available for host contact.

Colonization dynamics of algae in small artificial ponds

The arrival, establishment, and growth of a variety of algae were studied in a series of newly established, small (48.5 L) artificial ponds located at three sites of differing characteristics in southern Ontario, Canada: open field, edge of woods, and deep woods. Algal colonization was most rapid at the open site, within 4 days of the ponds being filled, and was slowest at the deep woods site, presumably because of a filtering effect of the surrounding terrestrial vegetation. The patterns of algal colonization and subsequent population abundances were consistent among the ponds, despite very considerable variation in both their physical and biological environments (e.g., among ponds over the 2 years of study, conductivity ranged from 20 to 890 μS, pH from 6.4 to 10.7, dissolved oxygen from 0 to 13.5 mg ∙ L−1, and water temperature from 5 to 29.8 °C). The first colonizers were airborne microchlorophytes, particularly a species of Chlorella, which may have been favoured by clear water (high light) conditions, lack of competition, and an ability to tolerate low nutrient levels. Chlorella populations declined within 1 or 2 weeks, depending on site, coincident with an increase in the numbers of a species of Synechococcus, a cyanobacterium. Synechococcus dominated all the pond types at all three sites thereafter, although its abundance was strongly correlated with water temperatures. In their 2nd year, undisturbed mature ponds developed encrusting algae, especially Rhizoclonium and Oedogonium, on their walls. In years 1 and 2, the densities of Synechococcus in both the new and mature ponds, respectively, were positively correlated with the larval densities of the dominant mosquito species Culex restuans. Synechococcus was the primary item in the diet of these insects. Key words: colonization, algae, habitat variability, Synechococcus sp., Chlorella sp., artificial ponds.

Landscape patterns of abundance of Ixodes scapularis (Acari: Ixodidae) on Shelter Island, New York.

Nymphal Ixodes scapularis Say, the vector of Lyme borreliosis, was most common in forested areas across Shelter Island, Suffolk County, New York, and least common in xeric habitats such as beach and grassland. At the scale of individual house yards, nymphs were most common at wooded edges of property and least common on lawns. The abundance of ticks at yard edges was positively correlated with numbers on lawns and in landscaping, suggesting that tick abundance in woods affects abundances in adjacent yards. Because 57% of all yard area is adjacent to woodlands on Shelter Island, public health efforts to reduce tick populations in wooded areas should supplement efforts by individual yard owners to decrease risk. Methods of tick control for woodlands should also be evaluated for their effect on tick populations in adjacent yard habitats.

Host-Seeking of Blaeklegged Tick (Acari: Ixodidae) Nymphs and Adults at the Woods—Pasture Interface

To clarify the risk of pastured livestock for exposure to Ixodes scapularis Say (Acari: Ixodidae), we estimated the host-seeking activity of nymph and adult blacklegged ticks at the woods-pasture interface on horse farms in Maryland. Parallel linear transects of 100 m length and 1 m width were sampled repeatedly in pastures and adjacent woodland locations during periods of nymph (early summer) and adult (fall and spring) host-seeking activity. Data collected over two successive years indicated that adults were most abundant in ecotonal vegetation at the wood's edge, median values of 6.4 and 2.2 ticks per 100 m2 sample during fall and 1.2 and 0.5 ticks per 100 m2 sample for spring periods. Nymphs were most abundant in the shallow woods location, median values of 4.2 and 35 ticks per 100 m2 sample, followed by the deep woods and wood's edge locations. Host-seeking nymph and adult black-legged ticks also were collected repeatedly in pasture vegetation, median values ranging from 0.2-0.8 ticks per 100 m2 sample, with a progressive decrease in abundance from the fenceline into pasture. Adults and nymphs both were uncommon more than 5 m into pastures, where only two adults and one nymph were captured in 84 (fall and spring) and 24 (summer) 100-m2 samples, respectively. Levels of adult and nymph host-seeking in pasture vegetation were spatially correlated with tick abundance in adjacent woodlands when ticks were numerous; this condition presumably reflects a spillover of ticks from the woodlands-based population. These findings expand knowledge of black-legged tick host-seeking behavior and establish a basis for the exposure of pastured livestock to nymphs and adults.

Ecology of the Himalayan Newt (Tylototriton verrucosus) in Darjeeling Himalayas, India

In Darjeeling district, West Bengal, India, Tylototriton verrucosus was found in 10 localities. It lives in rice fields, tea gardens, meadows underlying the shores of pools, at the edge of woods. Reproduction in March – May (sometimes up to September). Female parental care and tendency to terrestrial breeding were observed. Metamorphosis is commonly in August – October, but sometimes the larvae overwinter. This might be the result of a prolonged reproductive period. The age of animals was determined by counting annual layers in phalange transverse sections. The age of sexual maturation is supposed to be 3 – 5 (mostly 4) years. Maximum age estimated 11 years old. The duration of hibernation is 4 – 5 months. The larvae prey mainly upon small crustaceans and aquatic insects, aquatic adults prey on insects, earthworms, amphibian ova and larvae. Data on natural enemies and parasites are presented. Conservation problems are discussed.

Spatial variability of turbulent fluxes and roughness lengths in HAPEX-MOBILHY

Surface-based and aircraft measured fluxes over the heterogeneous surface in HAPEX-MOBILHY are analyzed for the ten flight days when cloud cover above the boundary layer was minimal. The fair-weather climatology of the spatial variation of surface fluxes is estimated to provide an assessment of the generality of previous case studies appearing in the literature. For the 10-day averages, greater heating over the forest generates a forest breeze which leads to rising motion and a modest increase of boundary-layer cloud cover at the forest edge. The exchange coefficients and effective roughness lengths are computed for local averages (15 km scale) and for regional averages (100 km scale) intended to represent a range of grid sizes in numerical models of the atmosphere. The effective roughness length for momentum over the mixed agricultural region for both scales is on the order of 1 m, apparently due to bluff roughness effects associated with scattered trees, edges of small woods and other obstacles. This roughness length value is an order of magnitude larger than values used in numerical models for the same region, which are based on the dominant vegetation type. The spatially varying effective roughness length for heat is computed for use in those models which use surface radiation temperature to estimate surface heat flux. The effective roughness lengths for heat are found to be smaller than those typically used in numerical models of the atmosphere.

Distribution of Ixodes dammini (Acari: Ixodidae) in residential lawns on Prudence Island, Rhode Island.

The distribution of nymphal Ixodes dammini Spielman, Clifford, Piesman & Corwin in residential lawns was assessed by flagging on Prudence Island, RI. The number of ticks per sample was five times greater in lawns adjacent to woods than in lawns adjacent to other lawns. Relative tick abundance was negatively correlated with distance from the woods, but the decline was gradual. Spirochete prevalence in ticks did not differ among lawn types or at different distances from the woods. Therefore, barriers that keep people away from the wood edge probably lower the risk of acquiring Lyme disease, but there is still a risk. Even with physical barriers at lawn-wood edges, personal precautions to prevent tick bites should be followed.

Influence of Landscape Structure on Abundance and Within-Field Distribution of European Corn Borer (Lepidoptera: Pyralidae) Larval Parasitoids in Michigan

Studies were conducted at eight locations in Ingham County, Michigan, during 1989–1990 to determine the within-field distribution of European corn borer, Ostrinia nubilalis (H¨bner), larval parasitism. O. nubilalis larval sampling was conducted at multiple locations on three transects across large 1st-yr corn fields during the F1 and F2 generations. Plants were destructively sampled to determine O. nubilalis abundance and larvae were returned to the lab to determine parasitism. Eriborus terebrans (Gravenhorst) (Hymenoptera: Ichneumonidae) was the dominant parasitoid of O. nubilalis in the sampled fields, accounting for 92.5% of the F1 and 99.2% of the F2 parasitism during 1989; and for 92.2% of the F1 and 99.1% of the F2 during 1990. Average parasitism by E. terebrans ( n = 4 fields) was 4.9 and 18.7% of F1, 10.2 and 9.1% of F2 larvae during 1989 and 1990 respectively. The maximum E. terebrans parasitism observed (37.4%) of the O. nubilalis larvae in one field (F1 1990), is the highest level reported for this species in the Midwest. Parasitism by E. terebrans during the F1 generation was greater along field margins than in field interiors in most fields during both years. During 1990, O. nubilalis larvae near wooded edges had significantly higher E. terebrans parasitism than those near nonwooded edges or field interiors. In the F2 generation, parasitism did not vary significantly from field margins to field interiors in either year. There was no consistent relationship between O. nubilalis larval density per infested plant and E. terebrans parasitism. These data suggest that local landscape structure, including proximity of particular noncrop habitats, plays an important role in the effectiveness of this natural enemy.

The Appalachian Firmoss, a New Species in the Huperzia selago (Lycopodiaceae) Complex in Eastern North America, with a New Combination for the Western Firmoss

The gemmiferous firmosses, containing the type species of Huperzia, Huperzia selago, are distinguished from the other members of Huperzia by concave-sided spores and specialized lateral branches consisting of gemmiphores and detachable gemmae. The species of the group hybridize and the hybrids possess abortive spores with spore fragments and undivided spore mother cells. In the past the systematic treatment of the species in this group has been unsatisfactory because no one has recognized the intermediate sterile hybrids. These can reproduce vegetatively by gemmae, often forming large populations. Undetected hybrid taxa muddle species boundaries by obscuring and combining the already subtle characters that differentiate species. The obviously abortive-spored hybrids have remained undetected by most botanists. Careful field study of sympatric populations of species and hybrids over the range of the taxa, as well as examination of over 6000 herbarium specimens, has resulted in the present alignment of species boundaries and the recognition of a new species, Huperzia appalachiana, in eastern North America. First, we will review the range and characters of the common firmoss species, and then present the range and characters of Huperzia appalachiana. Looking at the three major areas of overlap (the northern Appalachians, the southern Appalachians, and the north shore of Lake Superior), the consistency of characters will be examined as well as of hybrids. The shining firmoss, Huperzia lucidula, is an eastern North American endemic of moist conifer and deciduous forests and swamps, always with some shade. Common in the northern and eastern parts of its range, it extends north of the Great Lakes up into the boreal forest, south in the Appalachians to Georgia and Alabama, west in shaded moist sandstone ravines of Missouri and Arkansas and to the edge of the deciduous woods in Minnesota. It is a robust plant of indeterminate growth habit; the individual stems continue growing indefinitely, becoming decumbent with age and eventually rotting away at their base. The leaves are in annual zones of longer leaves and shorter leaves. The shortest leaves are bud leaves produced at the end of the growing season in the form of winter bud. In H. lucidula, the leaves of the two portions are similar in size and reflexed position. The long leaves are widest beyond the middle with serrate margins and, importantly, have no stomates on the upper surface. The gemmiphores and the gemmae are relatively large. The lateral lobes of the gemmae are broadly obtuse with an apiculate tip. The spores are relatively small, averaging about 25 gm.

Fox at the wood's edge: a biography of Loren Eiseley

Fox at the wood's edge: a biography of Loren Eiseley

Construction Tender Competition for Two Railway Viaducts

The Neugut Viaduct begins at the small Sagentobel River, crosses a main road (Überlandstrasse) and the Glatt River and then divides before reaching ground level in an industrial area. The main bridge, which is approximately 920 m long, has two railway tracks both ramps being some 600 m in length, and an elevated approach of some 260 m. The Weidenholz Viaduct, starts at the edge of small wood at Aegert between Kriesbachstrasse and the six-lane Federal Highway N1, crosses the N1 at an acute angle and descends into an industrial area. It is appropriate to ask if the conditions in such railway viaducts as Neugut and Weidenholz, which did not create opportunities for important project variations, were such that a submission competition rather than a limited project competition or a fixed contract approach needed organising. The solutions proposed were interesting and diverse both financially and from the construction point of view; they offered the owner a true alternative.

Nest Predation and Brood Parasitism of Tallgrass Prairie Birds

Rates of nest predation and brood parasitism on 5 bird species nesting in fragments of tallgrass prairies in Minnesota were affected by the size of the prairie fragment containing the nest, the distance from the nest to a wooded edge, and the number of growing seasons since the vegetation around the nest was last burned. Rates of nest predation for 5 species were lower (P < 0.10 in each case) for nests on large (-130 ha) fragments, in areas far (?45 m) from a wooded edge, and in vegetation that was recently burned (s3 yr). Rates of brood parasitism were lower (P < 0.10 in each case) far from a wooded edge. Prairie management to maximize nest productivity should provide large, regularly burned prairies with no nearby wooded edges. J. WILDL. MANAGE. 54(1):106-111 More than 99% of the presettlement tallgrass prairie in Minnesota has been converted to agriculture and other uses. Remnant tracts of prairie are usually small, isolated parcels surrounded by habitat unsuitable for most prairie birds. Many of the remaining prairie fragments contain invading tree species, such as aspen (Populus tremuloides) and willow (Salix spp.), and/ or cottonwood (Populus deltoides) shelterbelts. Natural fires, once common occurrences in the tallgrass prairie (Daubenmire 1968), are suppressed, but prescribed burning is now a major management activity on native prairies. Several animals that depredate or parasitize nests of prairie birds have recently increased in abundance in western Minnesota. For example, raccoons (Procyon lotor), nest predators once limited to southeastern Minnesota, have expanded their range into the prairie region and are now common (Hazard 1982). Densities of red fox (Vulpes vulpes) have increased due to changes in agricultural practices and the reductions of other canids (Johnson and Sergeant 1977). In addition, brown-headed cowbirds (Molothrus ater), an obligate brood parasite, have greatly increased in abundance since 1900 (Brittingham and Temple 1983). Currently, most management of prairie fragments is undertaken to perpetuate native plant communities, but little is known about how vegetation management affects breeding bird populations on prairies. Consequently, we studied the effects of nest predation and brood parasitism on the productivity of birds nesting in managed tallgrass prairies in western Minne-

PHENOLOGY, MOVEMENT, AND WITHIN-FIELD DISTRIBUTION OF THE GRAPE BERRY MOTH, ENDOPIZA VITEANA (CLEMENS) (LEPIDOPTERA: TORTRICIDAE), IN NEW YORK VINEYARDS

AbstractFrom 1976 to 1986, the average date of first male pheromone trap catch of grape berry moth was 20 May with an average degree-day (DD) accumulation (base 10 °C) of 150.1 (SE = 13.2). Fifty percent cumulative trap catch of the first generation of males averaged 334.1 (SE = 7.8) DD with an average date of 11 June. Degree-day accumulation was a more accurate method for predicting peak male trap catch than predictions based upon vine phenology and calendar date. Within-field distribution and levels of berry moth infestation were markedly affected by the surrounding habitat. Wooded edges or hedgerows were closely associated with an increase in the level of damage along vineyard borders and higher levels of overall infestation when compared with vineyards without wooded edges. Egg and larval infestation levels in wild hosts (Vitis spp.) were greater than those within adjacent commercial vineyards. Early in the season, male berry moth were trapped in high numbers in wooded areas adjacent to vineyards. After mid-July, males were trapped predominantly within vineyards and few were trapped in wooded edges. Movement of adults from wooded areas into vineyards is not suggested by observed patterns of female oviposition. Females oviposited primarily on wild hosts within the wooded areas and within the adjoining vineyard edges throughout the season.

Incidenza e relazioni tra flora apistica e gruppi corologici nel Friuli-Venezia Giulia

B/OGEOGRAPHIA — vol. XIII - 1987 Biageagrafia delle A/pi Sud-Orienta/i Incidenza e relazioni tra flora apistica e gruppi corologici nel Fiuli—Venezia Giulia (q‘) GUALTIERO SIMONETTI — RENZO BARBATTINI Irtituio dz‘ Dzfem delle Pzkzzzte, UI2z’z2em&#39;zfti dz’ Udzkze SUMMARY As part of a study being carried out on all the plants of apiarian interest in Friuli—Venezia Giulia an analysis was made of the spontaneous flora. The chorological elements were considered in relation to the distribution of single species at various altitudes. The most common chorological groups belong to the Eurimediterrenean orders (more than 50), followed closely (40-30) by the Eurasian, Paleotemperate, European-Caucasian, Circumboreal, South and Sout-East European. In mountain areas plants are mainly of the Orophite South European, European-Caucasian, Eurasian, Euro-Siberian and circumboreal types. In the foothills and lo\ver reaches of the mountains Eurasian, Paleotemperate, Eurimediterrenean plants are found, which is the most representative group of the east part of the Region (Gorizia, Carso, Trieste) together with the SE-European. There are few litoral (lagoon) species, though they are remarkably widespread and numerous. Keeping in mind the ecological niches, uncultivated and waste land has the largest number of millife- rous species (over 100), then follow the thickets, copses and edges of woods (over 50), next (between 40 and 50) plants of thermophylic woods, old ruins, hedgerows, vineyards, weeds. The diffusion of spontaneous melliferous, pollen and honey-de\v bearing species encourages a large scale permanent and migratory beekeeping in these different environments. Alongside the widespread production of heterofloral honey, thanks to the flowering of acacias and meadow wild flowers, it is possible to obtain also monofloral honey mainly from acacias, sweet chestnuts and dandelions. In this Region the flowers most favoured by migratory bee—keepers are the acacias and the sweet chestnuts, but removal of hives to the mountain areas to benefit from the flowering meadows and shrubs is becaming increasingly frequent. The apiarian importance of melliferous plants in certain areas is being notably reduced by the use of chemicals. The insecticides and fungicides used on agricultural ground can affect the pollinating insects attracted to spontaneous flower species. \Weed—killers can eliminate many melliferous plants both in culti- vated fields and along the waysides thus reducing the apiarian activity in that environment. RIASSUNTO Dall’analisi dell’insieme delle piante d’interesse apistico del Friuli—Venezia Giulia, di cui e in corso lo studio, tenendo conto solo della flora spontanea, sono stati presi in considerazione gli elementi corologici in rapporto alla distribuzione delle singole specie nei vari piani altitudinali. I gruppi corologici piu rappre— sentati sono nell’ordine le piante Eurirnediterranee (oltre 50), seguono poi, con presenze vicine (40-30) piante Eurasiatiche, Paleoternperate, Europeo—Caucasiche, Circumboreali, Sud e SE-Europee. Nel piano (*) Lavoro eseguito con il contributo del Ministero della Pubblica Istruzione (Progetto di Ricerca: «Indagini sullo stato dell’apicoltura in alcune regioni italiane per l’incremento della produzione». Coordi- natore Prof. Romolo Prota, Univ. di Sassari). 209

Habitat use by Red-tailed Hawks in surface-mined areas

Habitat use by 4 radio-tagged red-tailed hawks (Buteo jamaicensis) was monitored during 708 transmitter-days in coal surface-mined areas in northern West Virginia and southwestern Pennsylvania in 1977 and 1978. Mean cumulative home range size for the 3 adults was 316.8 ha (3.2 km2). Red-tailed hawks showed significant (P<0.005) tendencies to elect certain habitats over others. Descending order of habitat electivity was: 1) woods edge with open area not surfacemined. 2) woods edge with surface-mined area. 3) deciduous woods, 4) open area not surface-mined, and 5) surface-mined area. Red-tailed hawks' flexibility in niche requirements allowed them to exploit reclaimed area. Recommendations for surface mine reclamation are given.

Systematics of the Erigeron rusbyi Group (Asteraceae) and Delimitation of sect. Peregrinus

Erigeron rybius, sp. nov., is segregated from E. rusbyi sensu Cronquist and hypothesized to be the closest relative of E. coulteri. A key summarizes the differences among E. rybius, E. rusbyi, and E. arizonicus, which is the closest relative of E. rusbyi. These four species share several distinctive features with a larger group of 34 species here recognized as Erigeron sect. Peregrinus, section nov. The Asian species E. thunbergii and closely similar Asian forms are members of sect. Peregrinus. Possible relationships between sect. Peregrinus and the E. philadelphicus group and between sect. Peregrinus and a set of monocephalous, arctic and alpine species are considered, but there is not adequate justification for including them. Field and herbarium studies have led me to conclude that Cronquist's (1947) circumscription and discussion of Erigeron rusbyi were based on two species. The newly recognized species, described below, is strongly allopatric with E. rusbyi and comprises the population system cited by Cronquist from Otero and Lincoln cos., New Mexico. Erigeron rusbyi is provided with an emended description and is compared with its closest relative, E. arizonicus. Following that, the subgeneric group to which these species belong is delimited and named, with a discussion of some of the problems inherent in the taxonomy. Erigeron rybius Nesom, sp. nov., fig. 1.-TYPE: New Mexico, Otero Co., Sacramento Mountains, 1.6 km S of Cloudcroft on Hwy. 84, very abundant in clearing and along edges of white fir-Douglas firponderosa pine-Gambel's oak woods, 2520 m, 30 Aug 1981, G. Nesom 4535 (holotype: NY; isotypes: ARIZ, ASU, COLO, ENCB, GH, MEXU, NMC, OSC, OS, TEX, UNM, US). Proxime Erigeron coulteri Porter affinis, a qua foliis caulinis minoribus magis numerosis phyllariisque pilis nigro-septatis destitutis differt. Perennials from a system of very slender, woody, branching rhizomes with fibrous roots, producing erect stems and clusters of basal leaves at tips of slender stolons, produced singly, simple or less commonly with 1-2(-5) branches mostly on the upper Y2-Y3, these rarely branched, striateridged, moderately to densely pubescent with retrorse-spreading trichomes 0.3-0.8 mm long, sometimes slightly viscid with tiny, glandular, uniseriate trichomes. Basal leaves 1.8-13.5 cm long, blades 6-27 mm wide, elliptic-ovate to obovate, usually not strongly 3-nerved, serrate with 3-8 pairs of shallow, long-apiculate teeth, base attenuate to a wide petiole region ?4-?2 as long as the blade, apices acute, apiculate, less commonly obtuse to rounded; cauline leaves 9-14(-17), equably distributed, clasping, usually smaller than the basal but not strongly reduced in size up-

Effect of Spatial Distribution on Determining the Number of Samples Required to Estimate Populations of Hypera postica, Sitona hispidulus , and Hypera punctata1 for Specified Probability and Accuracy Levels 2

Sample size (required number of sample units), with specific consideration for spatial distribution and a dispersion parameter, was determined for adult Hypera postica sampled by 1-ft2 (929-cm2) alfalfa quadrats, and Hypera postica, Sitona hispidulus , and Hypera punctata adults sampled oy 1-ft2 emergence traps in wood edge aestivation sites. Taylor's power law ( s 2 = amb ), and the sample size equation N = (100/ c )2 t2 am b−2 provide an efficient means for this determination. Sample size-density estimate curves are presented for four probability (confidence) and three accuracy (precision) levels. Sample size was inversely proportional to adult weevil density in all cases except for S. hispidulus , where the sample size was directly proportional to density. At the 95% probability and 20% accuracy levels 1,173 quadrats are required to estimate an adult H. postica density of 0.1. A 40% accuracy level with this same probability level will estimate densities of H. postica as low as 0.3 per quadrat with only 100 samples.

Dynamics ofOstrya carpinifolia woods in the Southern Alps (N-Italy)

Forest regeneration in the vegetation complex of the submontane belt in the Southern Alps involves the active participation ofOstrya carpinifolia woods and their wood edge communities. The corresponding syndynamical processes are described by employing phytosociological, phytogeographical and ecological methods. It is concluded that: (i) The communities of the grassland-wood transition are of major importance in the successional developments in this man-made vegetation complex. (ii) Many species occurring in the region of the deciduous forests of Eurasia find their refuge in such transitional communities and are supposed to play an important part in the succession. (iii) Ostrya carpinifolia is considered as an early successional tree species.

Effect of Forest Clear-Cut Edge on Breeding Birds in East Texas

Effect of Forest Clear-Cut Edge on Breeding Birds in East Texas

Genetic changes in a population of fieldmice (Apodemus sylvaticus) during one winter

The ecological genetics of a population of fieldmice at the edge of a deciduous wood was studied over two years using starch‐gel electrophoresis and mark‐recapture techniques. Numbers fluctuated widely and the survival rates indicated a high degree of dispersal away from the grid in summer. In autumn 1974 a large influx of animals occurred when the adjacent fields were harvested. During the following winter significant changes in the phosphoglucomutase genotype frequency were observed, associated with a marked fall in numbers. Winter survival is normally good in Apodemus. These results are therefore of some interest.Either differential mortality or differential emigration could be responsible for the genetic changes. The former explanation is preferred in this situation. Fieldmice are known to exploit both field and wood habitats where they meet, and could be subject to differences in selection pressure in the two niches.