Interpatch movement of the red milkweed beetle,Tetraopes tetraophthalmus: individual responses to patch size and isolation

Individual movement patterns and the effects of host plant patch size and isolation on patch occupancy were examined for red milkweed beetles, Tetraopes tetraophthalmus, residing in a heterogeneous landscape. Male beetles were found to move both more often and farther between host plant patches than female beetles, and this difference affected the patterns of patch occupancy observed. Overall, unoccupied milkweed patches were smaller and more isolated than patches occupied by beetles. Patches uninhabited by females tended to be more isolated, but not necessarily smaller, than patches with female beetles, indicating that females may be affected more by patch isolation than patch size. Presence of male beetles on patches showed a stronger response to patch size than to patch isolation. Differences in movement between males and females illustrate the need for demographically based dispersal data. Comparisons of Tetraopes interpatch movement patterns between landscapes composed of patches of different size revealed that landscapes with overall smaller patches may have greater rates of interpatch movement.     

Population density and area: the role of between- and within-patch processes

The relationship between population density and the size of host plant patches was investigated for the red milkweed beetle Tetraopestetraophthalmus inhabiting unmanipulated patches of Asclepias syriaca. The resource concentration hypothesis proposes that density-area patterns, specifically that of increasing herbivore density with patch size, are primarily a function of movement between host plant patches. This research investigated the degree to which movement accounted for density-area patterns. Poisson regression analysis of beetle abundance versus milkweed patch size revealed that beetle density tended to increase with patch size. The pattern of density and patch size resulted from local reproduction and residence time. The density of emerging beetles tended to increase with patch size while emigration rates were unrelated to patch size. Immigration rates were constant with patch size for male beetles, and decreased with patch size for female beetles. Net flux of beetles (immigration – emigration) did not vary with patch size for male beetles and decreased with patch size for female beetles. Comparisons are made between this system and previously studied systems where movement plays a significant role in forming density area patterns. Additionally, several hypotheses are presented which may account for greater in situ recruitment and residence time in large patches. Received: 23 February 1996 / Accepted: 8 January 1997     

Changes in landscape structure decrease mortality during migration

I examined the dispersal of the red milkweed beetle, Tetraopes tetraophthalmus, among patches of its host plant, common milkweed, Asclepias syriaca. Over a 5-year period, the number of patches in a landscape and their mean size increased, while the distance between patches decreased. Over the same period the proportion of beetles dispersing between patches increased from 0.48 to 0.62. Estimates from the virtual migration model showed that mean migration distance decreased from 158 to 72 m for male beetles and from 129 to 72 m for female beetles. Estimated mortality per migration event decreased as the landscape changed, but was low in all years. The estimated mean migration mortality per patch decreased from 1.45 × 10⁻² to 3.70 × 10⁻⁷ for male beetles. Female migration mortality decreased from 5.48 × 10⁻³ to 3.88 × 10⁻⁶. Increasing the size and number of patches and decreasing interpatch distance decreases migration mortality and may play an important role in the conservation of species, particularly where mortality during dispersal is high.     

Some consequences for a parasitic herbivore,the milkweed longhorn beetle,Tetraopes tetrophthalmus,of a host-plant shift from Asdepias syriaca to A. verticillata

Summary The impact of differences in host plants on individuals and populations of insect herbivores was investigated using the milkweed longhorn beetle, Tetraopes tetrophthalmus (Forster), larvae of which feed parasitically on host rhizomes. One host, Asclepias syriaca L., was larger in stem and rhizome diameter and grew in cooler soil than the other host, A. verticillata L. The major effects on beetles were retarded phenology at the cooler site and reduced size on the smaller host. Reduced size of beetles was correlated with several important individual attributes: reduced length of life, number of ovarioles, egg size, and a reduced probability of mating with large beetles. The population consequences of these characteristics, largely inferred from these observations, were little or no outbreeding in the small population on A. verticillata.     

Impact of Host Plant Connectivity,Crop Border and Patch Size on Adult Colorado Potato Beetle Retention

Tagged Colorado potato beetles (CPB), Leptinotarsa decemlineata (Say), were released on potato plants, Solanum tuberosum L., and tracked using a portable harmonic radar system to determine the impact of host plant spatial distribution on the tendency of the pest to remain on the colonized host plant or patch. Results confirmed the long residency time on the host plant and showed that close connection of the plant to neighboring plants hastened dispersal between plants. Tracking walking CPB for over 6 h in small potato plots revealed that all types of mixed borders tested (potato/bare ground, potato/timothy and potato/woodland) acted as a strong barrier and retained beetles within the patch. In another experiment in potato patches surrounded by bare ground borders, tracked walking CPB displayed similar behaviour for up to four days. The distribution of turning angles in the CPB walking paths was not uniform and corresponded to beetles following the edge rows of potato patches in response to the crop border barrier or reversing their direction as they reached the end of a row and therefore a border. Patch size had no or little effect on beetle retention in the patch. The relative distribution of counts of tagged beetles detected among small (16 m²), medium (64 m²) and large size (256 m²) patches of potato four days after initial release remained similar to that of numbers released. Even though mixed crop borders were a strong barrier to walking CPB emigrating from potato patches, the departure rate of beetles over time was high. Results suggest that the effect of mixed borders is largely limited to dispersal by walking and does not apply to beetles leaving host patches by flight. The manipulation of crop borders and patch size seem to have limited potential for the management of CPB emigrating from potato fields.     

Importance of habitat patch size for occupancy and density of aspen-associated saproxylic beetles

In Fennoscandian boreal forests, aspen (Populus tremula) is one of the most important tree species for biodiversity. In this study we explore how occupancy and density of beetles associated with dead aspen are related to habitat patch size and connectedness in a 45,000 ha boreal managed forest landscape in central Sweden. Patch size was estimated as amount of breeding substrate and connectedness as crown cover of living aspen in the surrounding landscape. The beetles were sampled by sieving of bark or by inspection of species-characteristic galleries in 56 patches with dead aspen. Six of nine aspen-associated species (Xylotrechus rusticus, Ptilinus fuscus, Mycetophagus fulvicollis, Cyphaea curtula, Homalota plana and Endomychus coccineus) showed a positive significant relationship between habitat patch size and occupancy. For all these species, except C. curtula, there was also a significant positive relationship between patch size and density. Connectedness was not retained as a significant variable in the analyses. Species not defined as aspen-associated constituted a significantly larger proportion of the total density of individuals of saproxylic beetles in smaller habitat patches than in larger patches. Richness of aspen-associated species was positively related to habitat patch size. Efforts in the managed forest should be directed towards preserving and creating larger patches of living and dead aspen trees and increasing the amount of aspen at the landscape level.     

THE PROBABILITY OF FIXATION OF A NEW KARYOTYPE IN A CONTINUOUS POPULATION

We investigate the probability of fixation of a chromosome rearrangement in a subdivided population, concentrating on the limit where migration is so large relative to selection (m ? s) that the population can be thought of as being continuously distributed. We study two demes, and one- and two-dimensional populations. For two demes, the probability of fixation in the limit of high migration approximates that of a population with twice the size of a single deme: migration therefore greatly reduces the fixation probability. However, this behavior does not extend to a large array of demes. Then, the fixation probability depends primarily on neighborhood size (Nb), and may be appreciable even with strong selection and free gene flow (≈exp(-B ≈ Nb√s) in one dimension, ≈exp(-B ≈ Nb) in two dimensions). Our results are close to those for the more tractable case of a polygenic character under disruptive selection.     

Community structure and demography of small-mammal populations in insular montane forests in southern India

bstract Small mammals were studied in insular montane forest patches in the Upper Nilgiris in southern India from February 1994 to September 1996. Nine patches were selected at two sites, one with a single large 600-ha patch, the other with several small patches ranging in size from 0.2 to 60 ha. The population characteristics and community structure of small mammals were studied in relation to patch size and habitat structure within the patches. The two most abundant species were Rattus rattus (2–36 individuals/ha) and Suncus montanus (0–11 individuals/ha), while the abundance of seven other species recorded were very low. The population characteristics of R. rattus examined were density, biomass, proportions of juveniles, sub-adults and adults, mean weight of all animals, mean weight of adults, sex ratio and persistence. The proportion of adults, sub-adults, mean weight of animals, and mean weight of adult males were correlated with patch size. Persistence of sub-adult females in the large patch was especially high. The density and biomass of other small-mammal species were also studied. Two indices of diversity, species richness and proportion of R.␣rattus were compared as measures of community structure. Seven habitat characteristics were measured; of these, canopy cover, canopy height and tree density were correlated with the size of the patch. Density and biomass of species other than R. rattus and proportion of R. rattus were correlated with canopy height. Density and biomass of species other than R. rattus were highest in smaller patches. While the population characteristics of R. rattus may be affected by patch size, the density of rare species may be influenced by factors related to lower canopy height. Migration between patches may be an important factor in maintaining populations in these patches. Received: 5 January 1998 / Accepted: 23 March 1998     

Patch size of forest openings and arthropod populations

Summary Five sizes of canopy openings (0.016 ha to 10 ha) were established in the Southern Appalachian Mountains in early 1982 to examine the initial patterns of plant and arthropod establishment across a size range of forest disturbances. Vegetation standing crop after the first growing season was considerably higher in large than small openings in apparent response to greater resource release (e.g., sunlight) in larger openings. Woody stump and root sprouts were the dominant mode of revegetation in each patch size. Forest dominants such as Quercus rubra, Q. prinus and Carya spp. were less important as sprouters in openings than several minor forest components (e.g., Robinia pseudo-acacia, Acer rubrum, Halesia carolina and Cornus florida). Arthropod abundance and community composition varied across the size range of forest openings. Arthropods from the surrounding forest readily utilized the smallest canopy openings (0.016 ha). All feeding guilds were well represented in these small openings and herbivore biomass and load (mg of herbivores/g of foliage) were much higher than in larger patches. In contrast, arthropod abundance and species richness were significantly lower in mid-size than smaller patches. The relatively sparse cover and high sunlight in mid-size openings may have promoted surface heat buildups or soil surface/litter moisture deficits which restricted arthropod entry from the surrounding forest. Arthropod abundance and species richness were higher in large than mid-size patches. The greater vegetation cover in larger openings may have minimized the deleterious effects on arthropod populations. However, the absence of population increases among these arthropod species maintained herbivore loads at very low levels in large patches. Our results suggest that arthropod abundance and diversity in sprout-dominated forest openings are highly dependent on the extent of environmental differences between patch and surrounding forest.     

What shapes local density? The importance of migration rates and local growth for density‐patch size relationships in two Cionus weevils

1. The relative effect of migration and local growth on the spatio‐temporal density‐distribution of two co‐existing herbivorous weevils, Cionus scrophulariae L. and C. tuberculosus Scop., in 32 host plant Scrophularia nodosa L. patches of varying sizes was investigated. 2. Predictions of the temporal development of the slope in the density‐patch size relationships were derived from a basic population model with scale‐dependent migration rates. The model indicated that the slopes in the density‐patch size relationships during the early season should be reflected by the net scaling of immigration and emigration rates, whereas the slopes during the later season should increase as a result of local growth. 3. Emigration rates of the weevils were estimated in a field experiment, were the weevils coexisted in space and time. These results were then combined with a previous estimate of immigration rates in order to determine the net scaling of migration rates. 4. The emigration rate differed between species, caused by different movement rates in small patches, which could explain differences in the general slope of the density‐patch size relationships of the weevils in the natural figwort patches throughout the summer. The slopes in the relationships in the early season were largely predicted by the net scaling of migration rates. The slope also increased in the later season for C. tuberculosus, whereas the slope decreased for C. scrophulariae. 5. It was concluded that the understanding of both inter‐ and intra‐specific variations in density‐patch size relationships of insect herbivores can be improved using population models incorporating scale‐dependent migration and local growth.     

PERSPECTIVE: THE THEORIES OF FISHER AND WRIGHT IN THE CONTEXT OF METAPOPULATIONS: WHEN NATURE DOES MANY SMALL EXPERIMENTS

We critically review the two major theories of adaptive evolution developed early in this century, Wright's shifting balance theory and Fisher's large population size theory, in light of novel findings from field observations, laboratory experiments, and theoretical research conducted over the past 15 years. Ecological studies of metapopulations have established that the processes of local extinction and colonization of demes are relatively common in natural populations of many species and theoretical population genetic models have shown that these ecological processes have genetic consequences within and among local demes. Within demes, random genetic drift converts nonadditive genetic variance into additive genetic variance, increasing, rather than limiting, the potential for adaptation to local environments. For this reason, the genetic differences that arise by drift among demes, can be augmented by local selection. The resulting adaptive differences in gene combinations potentially contribute to the genetic origin of new species. These and other recent findings were not discussed by either Wright or Fisher. For example, although Wright emphasized epistatic genetic variance, he did not discuss the conversion process. Similarly, Fisher did not discuss how the average additive effect of a gene varies among demes across a metapopulation whenever there is epistasis. We discuss the implications of such recent findings for the Wright-Fisher controversy and identify some critical open questions that require additional empirical and theoretical study.     

Effects of fragmentation on vascular plant diversity in a Mediterranean forest archipelago

Abstract

We analysed the effects of patch size and isolation on vascular plants in Quercus cerris forest surrounding Rome (Italy). We randomly sampled 96 plots within 18 forest patches with homogeneous environmental variables; the patches ranged from 1.4 ha to 424.5 ha and were divided into four size classes. We performed the analyses at the patch level using linear regression. At the size class level, the analysis of species richness response to fragmentation (area effect) was performed with ANOVA, while the effect on community composition was analysed by means of PERMANOVA. We also investigated which species could be used as indicator species for each size class. Lastly, to evaluate the advantages of conserving several small patches as opposed to few large ones, we used a cumulative area approach ranking forest fragments. The correlation between species richness and patch area was positive, with a significant difference between the “large” and “small” size classes, while analysis on community composition showed that “large” versus “medium” and “large” versus “small” were significantly different. Nemoral species were recognised as indicators in the “large” class, and shrub and edge species in the “small” class. Our results indicate that 10 ha may be a suitable forest size threshold for planning and conservation.     

Regional persistence of an endemic plant, Erigeron acer subsp. decoloratus, in disturbed riparian habitats

Regional persistence of species requires a positive balance between colonizations and local extinctions. In this study, we examined the amount of colonizations and extinctions and their likelihood as a function of patch size, isolation, and habitat characteristics of a riparian perennial plant, Erigeron acer subsp. decoloratus. We also studied the importance of patch dynamics to the regional population growth. Over five successive years, we counted the number of plant patches along 43 km of riverside. Most patches were small in area and population size. The annual finite growth rate in the number of patches varied between years, but the geometric mean was close to 1.0, indicating a viable patch network in spite of local extinctions. Extinction rate was highest on steep slopes and for small patches with few individual plants and a small patch area. When the patches were classified into different stage classes, the most common fate was stasis, i.e., the patch remained at the same stage. Patch survival and local, within-patch dynamics were most important during this five-year period. Between-patch dynamics (including colonization for example) accounted for 5–10% of annual transitions. The overall dynamics were relatively similar to those of other plant species subjected to riparian disturbance regimes. In the long run, the survival of the species depends on how well it is able to escape from competition from forest and meadow species and track the availability of suitable habitats. This kind of habitat tracking differs from classical metapopulation dynamics. In the former, local extinctions occur as a consequence of adverse changes in the habitat and recolonizations are rare, whereas metapopulation models assume a highly persistent habitat structure with frequent recolonizations. In this respect, the regional dynamics of perennial plants in disturbed riparian habitats may differ from classical metapopulations.     

Limited dispersal and its effect on population structure in the milkweed beetle Tetraopes tetraophthalmus

Summary The movement patterns of adult milkweed beetles, Tetraopes tetraphthalmus, were monitored via a mark-recapture technique. Movement or dispersal patterns were studied in two natural populations, one in which the host plant, Asclepias syriaca, was nearly continuously distributed over a 250×90 m area and another where Asclepias was distributed in 17 small discrete patches. In both populations dispersal distances resulting from the flight patterns of the adult beetles were quite short, averaging less than 40 m from the point of first encounter 10 days after marking. Males were shown to be more vagile than females. The distribution of dispersal distances collected from one of the populations was fit to three statistical distributions cited in the literature as expected from dispersal by many small-scale movements or observed in other species. It was found that an equation describing an exponential decay gave the best statistical fit to the data collected here for milkweed beetles. The data is discussed in the context of the effects of the limited dispersal power of the beetles and the distribution of suitable habitat on the population structure of Tetraopes.     

POPULATION DIVERGENCE IN SEXUAL ORNAMENTS: THE WHITE FOREHEAD PATCH OF NORWEGIAN PIED FLYCATCHERS IS SMALL AND UNSEXY

Models of sexual selection suggest that populations may easily diverge in male secondary sexual characters. Studies of a Spanish population of the pied flycatcher, Ficedula hypoleuca, and a Swedish population of the closely related collared flycatcher, F. albicollis, have indicated that the white forehead patch of males is a sexually selected trait. We studied the white forehead patch of male pied flycatchers (n = 487) in a Norwegian population over seven years. Males with large forehead patches were in general more brightly colored, but patch height was not correlated to body mass, body size, or parasite loads. Conditions during the nestling period did not seem to influence patch height as an adult. Patch height increased slightly from the first to the second year as adults, but then remained relatively constant at higher ages. Patch height was not related to survival. Year-to-year changes showed that males who increased in patch height also increased in body mass, suggesting that expression of the forehead patch may be partly condition dependent. However, changes in body mass explained only a small proportion of the variance in patch height between males. Thus, patch height would not be a good indicator of male quality. Furthermore, patch size was also not related to male ability to feed nestlings, indicating that females would not obtain direct benefits by choosing males with large patches. However, patch height could be a Fisher trait, but this requires heritability and there was no significant father-son resemblance in patch height. Comparisons of the males visited by each female during the mate sampling period indicated that chosen males did not have larger forehead patches than rejected males. Experimental manipulation of patch height did not affect male mating success. These results indicate that females do not use patch size as a mate choice cue. Finally, patch height did not predict the outcome of male contests for nestboxes, suggesting that the forehead patch is not an intrasexually selected cue of status. Norwegian pied flycatchers have smaller forehead patches than both Spanish pied flycatchers and Swedish collared flycatchers. We suggest that this pattern may be explained by the lack of sexual selection on the forehead patch in the Norwegian population as compared to the other populations, where the patch is apparently sexually selected. We discuss possible reasons for these population divergences, such as female choice on an alternative secondary sexual character (general plumage color) and speciation among Ficedula flycatchers.     

PHASE III OF WRIGHT'S SHIFTING BALANCE PROCESS AND THE VARIANCE AMONG DEMES IN MIGRATION RATE

Interdemic selection by the differential migration of individuals out from demes of high fitness and into demes of low fitness (Phase III) is one of the most controversial aspects of Wright's Shifting Balance Theory. I derive a relationship between Phase III migration and the interdemic selection differential, S, and show its potential effect on F_ST. The relationship reveals a diversifying effect of interdemic selection by Phase III migration on the genetic structure of a metapopulation. Using experimental metapopulations, I explored the effect of Phase III migration on F_ST by comparing the genetic variance among demes for two different patterns of migration: (1) island model migration and (2) Wright's Phase III migration. Although mean migration rates were the same, I found that the variance among demes in migration rate was significantly higher with Phase III than with island model migration. As a result, F_ST for the frequency of a neutral marker locus was higher with Phase III than it was with island model migration. By increasing F_ST, Phase III enhanced the genetic differentiation among demes for traits not subject to interdemic selection. This feature makes Wright's process different from individual selection which, by reducing effective population size, decreases the genetic variance within demes for all other traits. I discussed this finding in relation to the efficacy of Phase III and random migration for effecting peak shifts, and the contribution of genes with indirect effects to among‐deme variation.     

Population genetics of three at-risk tiger beetles Habroscelimorpha dorsalis dorsalis,H. d. media,and Ellipsoptera puritana

Many tiger beetles (Family Cicindelidae) are critically imperiled due to their dependence on small patches of suitable habitat that are frequently threatened by natural and anthropogenic disturbances. In the eastern United States, conservation of three tiger beetles - Habroscelimorpha dorsalis dorsalis, H. dorsalis media, and Ellipsoptera puritana - has been inhibited by the absence of population genetic information that is needed for effective recovery planning and potential reintroductions. Using microsatellite panels, we performed population genetic analyses and compared patterns in diversity and differentiation within and between taxa. Nearly all collections of the three taxa had less observed heterozygosity than expected under Hardy-Weinberg Equilibrium, and there was a strong latitudinal gradient in genetic diversity in H. d. dorsalis distributed along the eastern and western shores of the Chesapeake Bay. We also found clear spatial patterns of genetic differentiation which reflected strong isolation-by-distance within all three taxa and between collections of H. d. dorsalis and H. d. media. However, there was evidence of admixture in current (mouth of the Chesapeake Bay) and former (coastal New Jersey) contact zones of H. d. dorsalis and H. d. media. Taken together, our study suggests that relatively few adult tiger beetles may maintain many populations, and that gene flow among nearby habitat patches is common in all three taxa – a characteristic that may help tiger beetles persist in dynamic coastal environments. Results of our analyses can be used to support conservation and management by identifying the spatial scale of metapopulation connectivity and locating populations at the greatest risk of extirpation.

     

Clonal growth strategies in simultaneously persistent and expanding <Emphasis Type="Italic">Trifolium repens</Emphasis> patches

Plants with clonal growth can generate patches dominated by a single species. In time, patches can change and may fragment, form a ring, dissolve or both persist and expand. For patches to maintain their original habitat and simultaneously increase in size, ramets or clonal fragments must both promote local persistence inside the patch and grow out of the patch into new habitats. This study analyses simultaneously expanding and persistent Trifolium patches in a nutrient-poor lawn that is frequently cut, and where the Trifolium is competitively superior to the grass species. Trifolium primary stolon growth strategies were analyzed in relation to their location (border, middle, and center) inside the patch, and according to patch size (small, medium, and large). It was hypothesized that different growth strategies inside a patch can explain both persistent and expanding patch of Trifolium, and that growth strategies were different between patch sizes. Primary Trifolium stolons had two different growth strategies inside and at the border of patches: (i) stolons at the border were long, grew fast, had few lateral stolons, and grew out of the patch, while (ii) stolons inside the patch were smaller, grew slowly, and had more lateral stolons and a wide range of growth directions. Growth strategies were not different between patch sizes. The directional growth and the high growth rate at the border will increase the patch size with time, while the growth strategy near the center consolidates the patch in space and time, by placing ramets inside the patch. Different growth strategies near the center and on the border result in Trifolium patches that are simultaneously persistent and on the increase. The results also indicate a division of labor among primary Trifolium stolons in a patch.     

ON THE EFFECT OF FOUNDER EVENTS ON EPISTATIC GENETIC VARIANCE

Mayr (1963) proposed that small isolated propagules from a large panmictic population would occasionally undergo a genetic revolution due to loss of genetic variability. More recently Templeton (1980a) has suggested that founder events may be much more important in systems that have strong epistasis. Because of the work of these and other authors it becomes an interesting theoretical problem to study the distribution of epistatic variance in a population following a founder event. In the model presented here measures of coancestry (Cockerham, 1967, 1984; Cockerham and Weir, 1973; Weir and Cockerham, 1973, 1977; Tachida and Cockerham, unpubl.) are used to examine the effect of founder events on additive-by-additive epistasis. Using this approach, the coancestries, or intraclass correlations, within individuals and within demes, together with the genetic variance components in the ancestral population are used to obtain the variance within and among demes following a founder event. Examples are analyzed for single founder events of 1–25 individuals and multiple founder events of two individuals. Following a single founder event, the contribution of the additive variance to the variance within demes relative to the additive variance in the ancestral population is always less than one. However, the contribution of epistatic variance to the variance within demes relative to the epistatic variance in the ancestral population is always greater than one. Thus, while a founder event decreases the contribution of additive variance to the variance within demes, it increases the contribution of epistatic variance to the variance within demes. The contribution of epistatic variance to the variance among demes following a single founder event is not qualitatively different from the contribution of additive variance to the variance among demes. These results indicate that epistatic variance is less likely than additive variance to cause a genetic revolution following a single founder event. When populations undergo multiple founder events the situation changes considerably. Epistatic variance may contribute as much as four times its original value to the variance among demes, while additive variance can contribute maximally twice its original value to the variance among demes. Thus, epistasis, which is relatively unimportant following a single founder event, may have major evolutionary implications if drift is allowed to continue for several generations.     

Sexual dimorphism in between and within patch movements of a monophagous insect: Tetraopes (Coleoptera: Cerambycidae)

Summary Movements of milkweed beetles (Tetraopes tetraophthalmus and Tetraopes femoratus) were monitored using mark-release-recapture techniques to compare the within- and between-patch movement patterns of individuals in a naturally occurring population. Within-patch and between-patch movement patterns differ in both frequency and distance traveled for males and females of both study species. Males move farther than females and are more likely to move between patches. Individuals recognize and alter movement upon encountering patch edges. Results suggest that laboratory estimates of Tetraopes vagility give a misleading indication of actual dispersal.