Long-term movements of self-marked caddisfly larvae (Trichoptera: Sericostomatidae) in a California coastal mountain stream

1. Over 140 000 larvae of the case-building caddisfly Gumaga nigricula were self-marked as they incorporated glitter into small portions of their cases while reared in streamside troughs. These marked individuals were released into stream pools and their movements monitored in the dry season, when base flow was low and no spates occurred, and in the wet season when base flow was high and several spates occurred. 2. Of the 9,000–10 000 larvae released in each of two stream pools in the dry season, 4–20% (i.e. 377–1817 marked individuals) were observed on three sampling dates (4, 11 and 24 d after release). Most larvae (87–93%) remained within 4 m up- or downstream of the release line after 24 d. No larvae were found outside of the release pools, even after 37 d. 3. Of the > 120 000 larvae released in one stream pool near the beginning of the wet season, 408 larvae were recaptured 130–167 d later, a period that included 30 days of high flow associated with six spates. Estimated survivorship over this period was 0.7–6.2%; there was no relationship between survival and larval size at release. Most (75%) recaptured larvae were found in the pool where they were originally released. The remaining larvae were found downstream of the release pool. Larvae had generally dispersed only a short distance downstream of the release pool (median = 18 m, maximum = 222 m). In addition, four marked pupae were later found 436 m downstream of the release pool. 4. These results illustrate the sedentary nature of larval G. nigricula as well as the important role that high flow events play in larval mortality and dispersal. These case-building larvae move very little during low flow periods, even when food resources appear limiting. In contrast, the frequency and distance of larval dispersal are much greater during periods with high flow. 5. Our observations for G. nigricula support previously published inferences that larval dispersal within a stream can be limited for some aquatic insects. However, our observations also suggest that, even for a relatively sedentary species like G. nigricula, larval dispersal during periods with high flow may contribute significantly to gene flow within a stream reach.     

Atyid shrimps (Decapoda: Atyidae) influence the spatial heterogeneity of algal communities over different scales in tropical montane streams, Puerto Rico

1. Atyid (Decapoda: Atyidae) shrimps influence the distribution of algal communities over different scales in tropical montane streams of Puerto Rico. Within pools of an atyid-dominated stream, atyid shrimps enhanced patchiness in algal communities along the depth gradient. Algal bands occurred in shallow pool margins where atyids did not forage (< 3 cm below water surface), with significantly greater standing crop, taxon richness, and structural complexity than deeper areas. In deeper water, atyids reduced small-scale patchiness in algal community composition and maintained a low-growing understorey turf dominated by sessile diatoms (Bacillariophyta) and, sometimes, closely cropped, filamentous blue-greens (Cyanophyta).
2. Among pools of the atyid-dominated stream, atyids interacted with light to determine algal patchiness between stream margins and deeper areas. In sunny pools, algal standing crop was 140-fold greater in pool margins than in deeper areas where atyids foraged. In shaded pools, however, standing crop in pool margins was only 5-fold greater than in deeper areas. Effects of light on algal standing crop were greater outside atyid foraging areas than within, indicating that shrimp grazing overrides the positive effects of light.
3. In contrast to the atyid-dominated stream, algal communities in an atyid-poor stream were characterized by a high biomass of loosely attached epipelic diatoms and no depth zonation. Interstream rock and shrimp transplant experiments indicated that atyids significantly reduced algal standing crop and altered community composition on rocks from atyid-poor streams within 24 h. Results support the hypothesis that atyid shrimps play a major role in determining observed interstream differences in algal communities.     

Atyid shrimps (Decapoda: Atyidae) influence the spatial heterogeneity of algal communities over different scales in tropical montane streams, Puerto Rico

1. Atyid (Decapoda: Atyidae) shrimps influence the distribution of algal communities over different scales in tropical montane streams of Puerto Rico. Within pools of an atyid-dominated stream, atyid shrimps enhanced patchiness in algal communities along the depth gradient. Algal bands occurred in shallow pool margins where atyids did not forage (< 3 cm below water surface), with significantly greater standing crop, taxon richness, and structural complexity than deeper areas. In deeper water, atyids reduced small-scale patchiness in algal community composition and maintained a low-growing understorey turf dominated by sessile diatoms (Bacillariophyta) and, sometimes, closely cropped, filamentous blue-greens (Cyanophyta).
2. Among pools of the atyid-dominated stream, atyids interacted with light to determine algal patchiness between stream margins and deeper areas. In sunny pools, algal standing crop was 140-fold greater in pool margins than in deeper areas where atyids foraged. In shaded pools, however, standing crop in pool margins was only 5-fold greater than in deeper areas. Effects of light on algal standing crop were greater outside atyid foraging areas than within, indicating that shrimp grazing overrides the positive effects of light.
3. In contrast to the atyid-dominated stream, algal communities in an atyid-poor stream were characterized by a high biomass of loosely attached epipelic diatoms and no depth zonation. Interstream rock and shrimp transplant experiments indicated that atyids significantly reduced algal standing crop and altered community composition on rocks from atyid-poor streams within 24 h. Results support the hypothesis that atyid shrimps play a major role in determining observed interstream differences in algal communities.     

Hierarchical organization of genetic variation in the Costa Rican livebearing fish Brachyrhaphis rhabdophora (Poeciliidae)

I examined the geographic distribution of genetic variation in the livebearing freshwater fish Brachyrhaphis rhabdophora in northwestern Costa Rica as revealed by allozymes and mitochondrial DNA sequences. Allelic variability at 11 enzyme-coding loci surveyed across 12 localities revealed marked genetic differentiation among populations within drainages (0_P= 0.36) and among drainages within regions (0_D=0.17), but not between northern and southern geographic regions (0_R=– 0.02). Allozyme variation was hierarchically organized such that populations found within stream drainages were more similar to each other than to populations found in adjacent drainages, a result confirmed by cluster analysis. In contrast to the allozyme data, there was extremely little DNA sequence variation among populations in the mitochondrial control region (3 variable nucleotide positions out of 444 bp examined). The difference in genetic divergence between allozyme and mtDNA markers was unexpected and is discussed in terms of biogeographical colonization events and a molecular selective swéep on the mitochondrial genome, both processes that could explain the lack of mitochondrial variability in this highly subdivided species.     

Survival of caddis larvae in relation to their case material in a group of temporary and permanent pools

1. The occurrence of larvae of Limnephilus coenosus and L. vittatus (Trichoptera) was recorded in 103 rock pools both before and after the dry periods in spring–summer (April–May and July–early August), when a great number of the pools dried out. In early spring, 84% of the pools sampled contained larvae of at least one of the species. Limnephilus coenosus larvae were present in a higher proportion of pools that later dried out than in the permanent ones, while L. vittatus larvae were predominantly found in permanent pools. Larvae of both species were found together in 31% of the inhabited pools.
2. Laboratory experiments, designed to elucidate differential survival under drought conditions, demonstrated that the organic cases of L. coenosus larvae held water more efficiently than did the mineral L. vittatus cases. Full-grown (fifth instar) L. coenosus larvae also survived dry conditions better than did L. vittatus larvae. The higher survival of L. coenosus was due to a combination of drought-resistant case material and a higher survival ability of the larvae themselves.
3. Limnephilus vittatus larvae were restricted by their low capability to withstand desiccation, although case material and food were available for L. vittatus larvae in all pools. Absence of case material and high-quality food in many pools, however, restricted the presence of L. coenosus larvae, but this species did not suffer from heavy mortality because of desiccation and all pool populations of L. coenosus survived until pupation.
4. The differences in species composition in these temporary and permanent pools can be explained by the differential site selection by ovipositing females, as well as by larval survival. The intrinsically greater survival of L. coenosus larvae during drought, together with the water-retaining properties of the cases, allowed this species to exploit stressful and risky habitats, such as temporary pools.     

Survival of caddis larvae in relation to their case material in a group of temporary and permanent pools

1. The occurrence of larvae of Limnephilus coenosus and L. vittatus (Trichoptera) was recorded in 103 rock pools both before and after the dry periods in spring–summer (April–May and July–early August), when a great number of the pools dried out. In early spring, 84% of the pools sampled contained larvae of at least one of the species. Limnephilus coenosus larvae were present in a higher proportion of pools that later dried out than in the permanent ones, while L. vittatus larvae were predominantly found in permanent pools. Larvae of both species were found together in 31% of the inhabited pools.
2. Laboratory experiments, designed to elucidate differential survival under drought conditions, demonstrated that the organic cases of L. coenosus larvae held water more efficiently than did the mineral L. vittatus cases. Full-grown (fifth instar) L. coenosus larvae also survived dry conditions better than did L. vittatus larvae. The higher survival of L. coenosus was due to a combination of drought-resistant case material and a higher survival ability of the larvae themselves.
3. Limnephilus vittatus larvae were restricted by their low capability to withstand desiccation, although case material and food were available for L. vittatus larvae in all pools. Absence of case material and high-quality food in many pools, however, restricted the presence of L. coenosus larvae, but this species did not suffer from heavy mortality because of desiccation and all pool populations of L. coenosus survived until pupation.
4. The differences in species composition in these temporary and permanent pools can be explained by the differential site selection by ovipositing females, as well as by larval survival. The intrinsically greater survival of L. coenosus larvae during drought, together with the water-retaining properties of the cases, allowed this species to exploit stressful and risky habitats, such as temporary pools.     

Genetic structure in a montane mayfly Baetis bicaudatus (Ephemeroptera: Baetidae), from the Rocky Mountains, Colorado

1. Populations of a number of sub‐tropical stream insect species have been found to show unexpected patterns of genetic variation, with more differences between samples from the same stream than between whole streams or between subcatchments. Many samples also showed deviations from Hardy–Weinberg proportions. It has been proposed that these patterns result from limited numbers of matings contributing to a given stream reach, because adults emerge throughout the year, and low levels of larval drift between reaches. These patterns may be less likely in a northern hemisphere montane species with synchronous emergence of adults and high levels of drift. We tested the hypothesis that patterns of genetic variation in a montane mayfly from the Rocky Mountains, Colorado, would reflect a pattern of ‘isolation by distance’ with samples from the same creek being more similar than samples from different creeks and that deviations from Hardy–Weinberg proportions would be minimal. 2. Based on allozyme variation, the hypothesis of minimal deviations from Hardy–Weinberg proportions was not supported and there was no evidence of isolation by distance. Nevertheless the levels of differentiation among samples from within the same stream were less than those reported for most subtropical species. 3. Results from analysis of a fragment of the cytochrome oxidase gene (subunit 1) revealed contrasting patterns. The levels of genetic differentiation were an order of magnitude higher between streams than among samples within streams. In addition, although there was no significant isolation by distance effect overall, a nested clade analysis provided evidence for restricted gene flow with isolation by distance for some clades. 4. We suggest that these contrasting results may reflect the differences in male and female dispersal patterns. While differentiation at nuclear gene markers (allozymes) give information about both male and female dispersal, mitochondrial DNA markers reflect only female dispersal. We suggest that in this species, female dispersal may be more restricted, perhaps mostly along stream channels, whereas male dispersal is more widespread. An alternative explanation for the different results is the different evolutionary rates of the mitochondrial and nuclear markers.     

Spatial patterns of mitochondrial and nuclear gene pools in chamois (Rupicapra r. rupicapra) from the Eastern Alps

We have assessed the variability of maternally (mtDNA) and biparentally (allozymes) inherited genes of 443 chamois (Rupicapra r. rupicapra) from 19 regional samples in the Eastern Alps, to estimate the degree and patterns of spatial gene pool differentiation, and their possible causes. Based on a total mtDNA-RFLP approach with 16 hexanucleotide-recognizing restriction endonucleases, we found marked substructuring of the maternal gene pool into four phylogeographic groups. A hierarchical AMOVA revealed that 67.09% of the variance was partitioned among these four mtDNA-phylogroups, whereas only 8.04% were because of partitioning among regional samples within the populations, and 24.86% due to partitioning among individuals within regional samples. We interpreted this spatial pattern of mtDNA variability as a result of immigration of chamois from different Pleistocene refugia surrounding the Alps after the withdrawal of glaciers, rather than from topographic barriers to gene flow, such as Alpine valleys, extended glaciers or woodlands. However, this striking geographical structuring of the maternal genome was not paralleled by allelic variation at 33 allozyme loci, which were used as nuclear DNA markers. Wright's hierarchical F-statistics revealed that only < or =0.45% of the explained allozymic diversity was because of partitioning among the four mtDNA-phylogroups. We conclude that this discordance of spatial patterns of nuclear and mtDNA gene pools results from a phylogeographic background and sex-specific dispersal, with higher levels of philopatry in females.     

Interaction between insect larvae and tadpoles in tropical rain pools

Abstract. 1. Ephemeral rain pools on rock surfaces are common in Africa and are inhabited by dense populations of aquatic dipteran larvae. About 30% of the pools also support large numbers of tadpoles of the frog Ptychadena anchietae .
2. Experiments reveal that the presence of tadpoles suppress eclosion of the rock pool dwelling midge Chironomus imicola .
3. However, the presence of tadpoles also shortens the larval life-span of C. imicola by speeding up growth rates. Since the larval stages must be completed before the pool dries tadpoles may help 'fine-tune' the dipteran to the rock pool habitat.
4. A change in the diet of Cimicola larvae is associated with the accelerated development. Grazing by tadpoles results in algae, growing on the water surface, reaching the mud in tadpole faeces. These algae represent a high protein and energy food not otherwise accessible to mud dwelling dipteran larvae.
5. When pools dry tadpoles are killed, but a second species of dipteran Dasyhelea thompsoni have larvae able to survive to dry phase in situ . These larvae are scavengers so that on reflooding dead tadpoles are available as food. Experiments show that the presence of tadpoles again increase larval growth rates.
6. Both alive and dead tadpoles therefore are responsible for increasing the quality and quantity of food available to dipteran larvae and are thus among the mechanisms ensuring an abundance of food for rock pool dwelling insect larvae.     

Cryptic diversity in an endemic rainforest skink (Gnypetoscincus queenslandiae)

Gynpetoscincus is a monotypic genus of skink endemic to the ancient and biogeographically complex wet tropical rainforests of northern Queensland. Surveys of variation in mitochondrial DNA and allozymes inG. queenslandiae revealed a major genetic break within the skink's 275 km range, clearly dividing it into northern and southern populations. The genetic differences between the two groups of populations are several-fold greater than differences between similarly separated localities within the southern group. The presence of two strongly differentiated evolutionary lineages within this narrowly distributed species highlights the value of genetic surveys to estimate evolutionary diversity in old, biogeographically complex biomes such as these rainforests.     

Limnological observations of an intermittent tropical dry forest stream

This study examines aspects of the seasonal limnology of an intermittent stream in the dry forest region of northwest Costa Rica. It focuses on annual water level fluctuations and both seasonal and among pool variation in dissolved oxygen concentration and water temperature. Dry season pools differed in morphometry and the rate of decline in water levels subsequent to the seasonal floods. Rate of water level decline was related both to pool depth and to the exposure of the pool to the sun. Oxygen concentration was generally low in the dry season, but increased during the rainy season in association with rain events and seasonal flooding. A repeated-measures analysis of variance indicated that seasonal effects accounted for 40% of the variance in oxygen concentration for residual pools. Differences among pools were also significant. However, there was strong evidence for a significant interaction between seasonal and spatial influences on oxygen values in the system. Variation in water temperature was small, but differences among pools, sampling dates, and their interaction were all significant. Periphyton production increased significantly between the late wet season sample in November and the dry season sample in February. Incident light intensity explained 76% of the variation among pools in net periphyton production in the dry season.     

Ecology of leptocerid caddisfly larvae in an intermittent South Australian stream receiving Eucalyptus litter

SUMMARY. 1. Brown Hill Creck, a small intermittent stream in dry sclernphyll forest in South Australia, flows for about 6 months during winter and spring. When flow ceases the stream dries to isolated pools which receive high summer inputs of Eucalyptus obliqua litter. Decomposition of this material in remnant pools causes extremely dark waters and depressed oxygen concentrations for up to 90 days.
2. Only two fully aquatic insect species, Lepntorussa darlingtoni and Lectrides varians (Trichoptera: Leptoceridae), persist under these conditions. Both utilize litter as food, but have different feeding strategies. The more abundant L. darlingtoni ingests organic and microbial material from leaf surfaces, whereas L. varians is a leaf shredder.
3. Larval processing budgets based on laboratory and fleid experiments indicated that L. variant has a greater impact on litter decomposition rates than L. darlingtoni . However, because of low density, low oxygen concentrations in pools during summer, and rapid flushing of litter from pools once flow recommences. L. variaus larvae process a small proportion of the total litter input.     

Individual growth variation of red-spotted masu salmon,Oncorhynchus masou rhodurus,in a mountain stream

Individual growth patterns in red-spotted masu salmon,Oncorhynchus masou rhodurus, were examined by mark and recapture in a mountain stream, central Japan. The growth pattern varied substantially among individuals of the same age cohort in the stream. Mean absolute growth rates of the individuals were neither significantly different between years, study sections along the stream course, or sexes, but showed significant differences between seasons. No correlation was found between the individual growth rate of fish and the area of pools they inhabited. However, there was considerable growth variation among inhabitants of the same pool. Within a pool, larger individuals grew more rapidly than smaller ones, despite there being no significant relationship between individual growth rates and initial body weights in the stream overall. Individual growth differences probably resulted from growth depensation caused by intraspecific competition within individual pools.     

Developmental Variation in Amylase Allozyme Activity Associated with Chromosome Inversions in DROSOPHILA PERSIMILIS

The amylase locus in Drosophila persimilis is polymorphic for allozymes, two of which show associations with naturally occurring chromosome 3 inversions. Amy1.09 occurs at high frequencies only in Whitney (WT), while the other common arrangements-Standard (ST), Klamath (KL) and Mendocino (MD)-are predominantly Amy 1.00. We have examined numerous strains, representing various electromorphs and inversions, for variation in cis-specific activity expression in both third-instar larvae and adults. Comparisons of these two life stages also allows the survey of developmental variation in amylase activities. The amount of activity variation exceeds electrophoretic variation at this locus. Moreover, this variation is largely nonrandom and reveals more genic divergence among inversions. The 1.00 allozyme of MD is more active than 1.00 KL in larvae and adults and shows a different developmental pattern. The activity of the 1.00 allozyme of KL is greater than 1.00 allozyme of ST in larvae and adults, but these two arrangements have similar developmental patterns. WT 1 with a 1.00 allele is dramatically different from the 1.00 allozymes of other arrangements in its developmental pattern. The 1.09 allozymes has high activity in WT and KL, but these arrangements differ in their developmental pattern of expression, WT being more active in adults. F2 segregational analyses are consistent with the variation being due to either structural enzyme variants or closely linked cis-acting regulatory elements. We argue that the suppression of recombination between arrangements has allowed the divergence in amylase activity among inversions.     

Effects of deforestation on fish community structure in Ecuadorian Amazon streams

SUMMARY 1. There is little information on the impacts of deforestation on the fish fauna in neotropical streams, and on parameters influencing species diversity and community structure of fish. We analysed these aspects in 12 stream sites in the Ecuadorian Amazon. The stream sites represented a large gradient in canopy cover and were located in an area of fragmented forest. While some streams had been deforested, they had not suffered gross degradation of the habitat.
2. The species richness of stream fish was not related to deforestation. Local fish diversity (Fisher's Alpha) was positively related to the surface area of stream pools (m²). Beta diversity was higher among forested than deforested sites, indicating greater heterogeneity in species composition among forested than deforested sites. The percentage of rare species was positively correlated with canopy cover.
3. Total fish density increased with deforestation, and the fish community changed from dominance by omnivorous and insectivorous Characiformes at forested sites to dominance of periphyton-feeding loricariids at deforested sites.
4. Multidimensional statistical analysis of fish community structure showed that six environmental variables (the area of stream bottom covered by leaves, relative pool area, particulate organic matter, mean depth, conductivity and suspended solids) were related to the ordination axes. The presence of leaves, which was strongly correlated to canopy cover, was the variable most closely related to fish community structure, while relative pool area was the second strongest variable. Thus, fish community structure was strongly affected by deforestation.     

Do stream macroinvertebrates use instream refugia in response to severe short-term flow reduction in New Zealand streams?

1. Demand for water is increasing and water managers need to know how much they can remove from a stream before there are significant detrimental effects on its biological integrity. Flow reduction alters a number of habitat variables known to be important to aquatic invertebrates such as depth, velocity, temperature and fine sediment accumulation. Some taxa may attempt to use instream refugia to mitigate the effects of flow reduction.
2. We experimentally manipulated flows by constructing weirs and diversions in three small New Zealand streams. Discharge was reduced by 88–96%. We tested the hypothesis that macroinvertebrates would use pools and the hyporheic zone as refugia during short-term (1-month) periods of reduced flow.
3. We sampled hyporheic invertebrates with colonization chambers and pool invertebrates with kick nets within a before-after, control-impact (BACI) experimental design. A suite of physicochemical parameters was measured concurrently including surface and hyporheic temperatures.
4. Flow reduction significantly decreased velocity (60–69%) in all streams. Depth (18–61%) and wetted width (24–31%) tended to decrease but these changes were not always significant. Sediment cover increased the most in farmland streams (10–80%). Apart from decreasing temperature range (18–26%), flow reduction had little impact on the surface water temperatures.
5. Flow reduction had no impact on the abundance of common pool macroinvertebrates or on the abundance, vertical distribution or community composition of hyporheic macroinvertebrates.
6. Our results suggest that aquatic macroinvertebrates are resistant to short-term, severe flow reduction as long as some water remains.     

Flexible oviposition strategies in túngara frogs and their implications for tadpole spatial distributions

Because oviposition site selection is often studied in a single ecological context, little is known about flexibility in oviposition strategies. We studied the oviposition site selection strategies of túngara frogs ( Physalaemus pustulosus ) with respect to conspecific eggs and larvae in two different ecological contexts-arrays of artificial ponds and natural stream pools. We fit maximum likelihood models to sequential pond use data for both systems and found that strategies for oviposition differed greatly between the two systems. Within arrays of artificial ponds, túngara frogs avoided both conspecific egg masses and conspecific larvae. However, within a set of natural stream pools, túngara frogs consistently oviposited in the same pools from night to night, while many nearby ponds went unused. These variable strategies produced very different distributions of tadpoles among ponds, such that tadpoles tended to be evenly spread among artificial ponds, but highly clumped within stream pools. The difference between the two strategies appears to be an overriding effect of habitat quality. Surface area and the amount of leaf litter were all significant predictors of whether stream pools were used. Additionally, an experiment in which egg masses were either transplanted to, or removed from, selected stream pools provided no evidence that frogs in these pools used egg masses per se as a cue for oviposition. These results illustrate that oviposition strategies may be very flexible, allowing species to adjust strategies to different ecological contexts. Furthermore, they demonstrate that variation in oviposition strategies may have strong effects on egg and larval spatial distributions in patchy environments.     

A comparative analysis of population structuring and genetic diversity in sympatric lineages of freshwater shrimp (Atyidae: Paratya): concerted or independent responses to hydrographic factors?

1. We determined whether two sympatric mitochondrial DNA (mtDNA) lineages of freshwater shrimp (Decapoda: Atyidae: Paratya australiensis) represent biological species and if they had concerted or independent population responses to hydrographic factors in small streams (the Granite Creeks) in southeastern Australia. 2. Allozyme data indicated the presence of two gene pools at sites where the P. australiensis lineages were co‐occurring and the gene pools were statistically assigned with high probability to each respective lineage. This indicated that these mtDNA lineages in P. australiensis were reproductively isolated and thus biological species. 3. Populations of both lineages were genetically homogeneous among lowland sites within streams, but were isolated by steep stream gradients among upland sites and for lowland–upland site comparisons. However, the magnitude of differentiation was markedly different between the two lineages. Allozyme diversity also differed between the two lineages, suggesting that they have different effective population sizes. Thus, differences in the magnitude of genetic divergence among populations were probably because of different life‐history characteristics, including dispersal ability and population size. 4. Genetic population structure was mostly temporally stable, despite the extreme effects of drought during the first year and substantial stream‐flow during the second. However, stable isotope analyses revealed greater local movement in both lineages during the second year, as greater hydrological connectivity provided more opportunities for dispersal. Thus, although lowland populations within streams were genetically homogeneous, stable isotope data indicated that connections may be sporadic and result from accumulated small‐scale movements among refugial pools. 5. Both lineages were therefore found to have similar small‐scale population responses to the unstable habitats of the Granite Creeks. Results highlight the importance of refugia for the capacity of biota to recover from drought and the need for multiple restored patches to reinstate natural population processes (e.g. resilience, recolonization) in degraded systems.     

Spatial heterogeneity of mitochondrial DNA and allozymes among populations of white-tailed deer and mule deer.

A white-tailed deer (Odocoileus virginianus) population in northeastern Minnesota and a mule deer (O. hemionus) population in the Bridger Mountains Montana, have previously been shown to be spatially subdivided into contiguous subpopulations. We assessed the degree of genetic differentiation among subpopulations and tested the hypothesis that differentiation will be greater for mitochondrial DNA (mtDNA) than for nuclear-encoded allozymes. Differentiation of the white-tailed deer subpopulations was significant for two allozyme loci but not for mtDNA, and the overall degree of differentiation was low. Gene flow, recent founding of the subpopulations, and polygamous breeding structure may all have contributed to this pattern. Greater differentiation was evident among disjunct populations than between the contiguous subpopulations of white-tailed deer. The contiguous mule deer subpopulations were significantly differentiated for mtDNA and one allozyme locus. Differentiation was greater for mtDNA than for allozymes. These results are consistent with demographic data that indicate mule deer males disperse more than do females. Disjunct mule deer populations may be similar or dramatically different in mtDNA haplotype frequencies that do not necessarily vary with geographic distance. Current and historical gene flow and breeding structure will influence population genetic patterns.     

Genetic relationships among populations of wild resident, and wild and hatchery anadromous brook charr

To determine the genetic relationship of anadromous and resident life-history types within and among drainages, and compare several hatchery strains to their progenitor populations, brook charr Salvelinus fontinalis were examined for allozyme and mitochondrial DNA variation. Greater genetic similarity of sympatric anadromous and resident charr was found compared to similar life-history forms allopatrically, suggesting the two life-history types are not reproductively isolated. Low divergence among the mtDNA haplotypes suggests that the two life-history types are members of the same evolutionary lineage. Population differentiation from mtDNA data exceeded that from estimates based on allozymes. Genetic deviations from expectations suggest that the hatchery strains were derived from few individuals.