Black bears in Southeast Alaska: the fate of two ancient lineages in the face of contemporary movement

Biodiversity across a landscape is a product of both historical events and ongoing contemporary forces. The past and present factors that influence black bear Ursus americanus diversity on the Alexander Archipelago and mainland of Southeast Alaska were investigated by assessing nuclear genetic variation. The natural fragmentation of the region, the high vagility of black bears and their possible recent post-Pleistocene colonization to Southeast Alaska allowed us to discern between past and present forces characterizing diversity. Two known black bear lineages, estimated previously with mitochondrial DNA to have diverged 1.8 million years ago, remained evident in data from more rapidly evolving nuclear genetic markers. Two nuclear genetic clusters geographically correspond to the lineages, suggesting that contemporary movement since colonization (likely beginning 18 000 cybp) has not been sufficient to eliminate genetic differences between the highly divergent lineages. Concomitantly, the clearest pattern of genetic diversity is related to contemporary geographic patterns; contemporary geography differs from geography immediately after deglaciation due to sea-level change. Narrow saltwater straits, expansive ice fields, narrow beach fringes and saltwater inland bays separate genetically distinct groupings of black bears.     

Changes in abundance of Vespula germanica and V. vulgaris in England

1. Thirteen time series, varying from 17 to 27 years, of the abundance of Vespula germanica and V. vulgaris from lowland England are examined. The time series depend on either spring queens and workers taken in Malaise or suction traps, or collected colonies. 2. During the late 1970s and early 1980s, the abundance of V. germanica declined abruptly but that of V. vulgaris did not. 3. During the early 1980s, the 2‐year cycle of annual abundance of V. vulgaris changed to a nearly perfectly damped pattern of annual abundances. 4. The most likely factor causing these population changes was the increased use of pesticides acting directly by killing the wasps and indirectly by reducing their food resources. 5. The difference in response of the two species to increased pesticide use may be related to a difference in foraging ability.     

Analysis of mtDNA indicates weak temporal genetic heterogeneity in pink salmon spawning runs in two rivers on Sakhalin Island

Both odd- and even-year pink salmon populations were sampled during the spawning runs in Firsovka and Bakhura rivers on Sakhalin Island. Four collections of 30 fish spaced at 2-week intervals were taken from each river in 2 consecutive years. Four restriction endonucleases were used to examine 2·15% of the mitochondrial genome. Eighteen variable sites and three types of insertion defined 37 haplotypes among 449 fish. Heterogeneity tests showed highly significant differences among temporal collections taken in the odd year from Bakhura River, and no significant differences among temporal collections from the other three spawning runs. However, probabilities of homogeneity among temporal collections were low in all tests, and an integral estimate of the probability of homogeneity for the total set of tests was less than 0·001, indicating highly significant overall temporal heterogeneity. Analysis of molecular variance (AMOVA), revealed that a small portion of the variance was distributed among temporal collections, and small φ_ST values that differed significantly from zero only in the odd-year population in Bakhura River. Temporal differences in spawning are probably adapative, and allow greater productivity in areas of high spawning densities.     

Density-dependent melanism in sub-arctic populations of winter moth larvae (Operophtera brumata)

Abstract.  1. The aim of this 4-year observational study was to test for the presence of direct and delayed density-dependent larval melanism in the geometrid moth species Operophtera brumata (winter moth) in northern Norway.
2. Data from many populations with a wide range of population densities in time and space facilitated statistical analyses that could separate the effects of current and past density. The data also included different phases of the 10-year population cycle of this species so that eventual non-linear density effects due to population phase could be detected.
3. The results showed that the prevalence of melanism had a strong positive, linear relation to population density within years, whereas there was no evidence for a delayed effect from the year before or dependency on the phase of the population cycle.
4. In combination, these results limit the range of possible explanations of larval melanism in this outbreaking species. The possible reasons why winter moth larvae might benefit from crowding-induced melanism are discussed.