Paweł Mirski

Unexpected population genetic structure of European roe deer in Poland: an invasion of the mtDNA genome from Siberian roe deer

Introgressive hybridization is a widespread evolutionary phenomenon which may lead to increased allelic variation at selective neutral loci and to transfer of fitness‐related traits to introgressed lineages. We inferred the population genetic structure of the European roe deer (Capreolus capreolus) in Poland from mitochondrial (CR and cyt b) and sex‐linked markers (ZFX, SRY, DBY4 and DBY8). Analyses of CR mtDNA sequences from 452 individuals indicated widespread introgression of Siberian roe deer (C. pygargus) mtDNA in the European roe deer genome, 2000 km from the current distribution range of C. pygargus. Introgressed individuals constituted 16.6% of the deer studied. Nearly 75% of them possessed haplotypes belonging to the group which arose 23 kyr ago and have not been detected within the natural range of Siberian roe deer, indicating that majority of present introgression has ancient origin. Unlike the mtDNA results, sex‐specific markers did not show signs of introgression. Species distribution modelling analyses suggested that C. pygargus could have extended its range as far west as Central Europe after last glacial maximum. The main hybridization event was probably associated with range expansion of the most abundant European roe deer lineage from western refugia and took place in Central Europe after the Younger Dryas (10.8–10.0 ka BP). Initially, introgressed mtDNA variants could have spread out on the wave of expansion through the mechanism of gene surfing, reaching high frequencies in European roe deer populations and leading to observed asymmetrical gene flow. Human‐mediated introductions of C. pygargus had minimal effect on the extent of mtDNA introgression.

Water regime as a key factor differentiating habitats of spotted eagles Aquila clanga and Aquila pomarina in Biebrza Valley (NE Poland)

Capsule Foraging sites of Aquila clanga compared to Aquila pomarina are characterized by a considerably longer duration of flooding within the year and higher mean and maximum depths of flooding. A. clanga is particularly associated with shallow (approx. 20 cm) spring flooding, lasting at least up to the beginning of May (on average up to 90 days per year). Variation in habitat selection with respect to water regime might be due to different food preferences and adaptation to landscape differences in the ranges of these two species.

Effect of selected environmental factors on hunting methods and hunting success in the lesser spotted eagle Aquila pomarina in North-Eastern Poland

Hunting methods and hunting success and their associations with some environmental factors were studied in Lesser Spotted Eagle. Birds hunted mostly by patrol-flights (73.6%), secondary by perchhunting (23.8%). In the morning-noon period birds hunted using patrol flights more frequently than in the afternoon, while in the afternoon they more often used perch-hunting. Average hunting success reached 24% (n = 37), but it was much greater on freshly mown meadows.

Purifying Selection, Density Blocking and Unnoticed Mitochondrial DNA Diversity in the Red Deer, Cervus elaphus

The trajectories of postglacial range expansions, the occurrence of lineage patches and the formation and maintenance of secondary contact between lineages may mostly reflect neutral demographic processes, including density blocking, that may leave long-lasting genetic signatures. However, a few studies have recently shown that climate may also play a role. We used red deer, a large, mobile herbivore that is assumed to be sensitive to climate change, to test hypotheses of possible selection on the mitochondrial DNA cytochrome b gene (mtDNA cytb) and competitive and/or density-blocking (using mtDNA control region). We searched for a possible link between the phylogeographic structure and abiotic climatic variables. Finally, we tested for isolation by distance and isolation by environment and assessed the impact of human-mediated translocations on the genetic structure of red deer. Our analysis of 30 red deer populations in Poland using the mtDNA control region (N = 357) and cytochrome b (N = 50) markers not only confirmed the presence of the Western and South-Eastern lineages of the species but also indicated the presence of a previously unnoticed, rare relic haplotype that grouped together C. e. italicus from Italy (the Mesola deer). No significant signs of positive selection were detected for the mtDNA cytb gene in the studied red deer. However, a significant signal for purifying selection was found in our study that may explain the narrowness of the contact zone because gene flow between the Western and South-Eastern lineages should drive relatively strong mito-nuclear incompatibilities. MtDNA control region differentiation among red deer populations in Poland correlated with different abiotic climatic variables. Strikingly, the southernmost ice sheet limits during the Elsterian was the most important factor, and it explained the largest amount of variation. However, neither isolation by distance (IBD) nor isolation by environment (IBE) were recorded, and a very limited impact of human translocations was evident. The above-mentioned results suggest that in contemporary red deer populations in Poland, the phylogeographic pattern is well preserved, and long-term processes (density and/or competitive blocking) still play a major role.

Seasonal and spatial variation of the Montagu’s Harrier’s Circus pygargus diet in Eastern Poland

Capsule: The diet of the Montagu’s Harrier Circus pygargus is variable and comprises the most available prey at a given time of the season. We found no evidence for a relationship between diet and land-use in the core foraging zone. Aims: We investigated whether the diet of the Montagu’s Harrier reflects the available prey and how it changes across the breeding season and in relation to land-use. Methods: We analysed pellets collected at nests between 2007 and 2011. We looked for nonlinear patterns in the occurrence of prey categories in the pellets as a nonlinear function of the Julian date. Moreover, we tested whether the diet is affected by land-use within a radius of 2299 m from the nest. Results: Four thousand four hundred and sixty-five prey items were found in 880 pellets and 76 prey remains collected at 63 sites. The diet did not depend on the land-use structure but showed a significant temporal variation. Conclusions: The diet of the Montagu’s Harrier follows the availability of the prey in the foraging habitat. We conclude that the type of land-use in the vicinity of the nesting habitat has a rather weak effect on the diet of the Montagu’s Harrier.

Genetic structure of dioecious and trioecious Salix myrsinifolia populations at the border of geographic range

Gene flow in plant populations is heavily affected by species sexual systems. In order to study the effect of sexual systems on genetic structure, we examined plastid and nuclear DNA of 12 dioecious (males and females) and 18 trioecious (males, females and hermaphrodites) populations of Salix myrsinifolia—a boreal shrub with slow range expansion. Populations were located along latitudinal gradients across submarginal and marginal parts of the range. Individuals of each sex morph were all hexaploid. We identified 10 chloroplast DNA haplotypes and scored 205 polymorphic bands with amplified fragment length polymorphism. We found dioecious populations that differed from trioecious populations via the presence of four unique haplotypes and significant difference in Nei’s gene diversity index (0.119 vs. 0.116) and down-weighed marker value (1.17 vs. 1.02). The latter parameter, together with haplotype and nucleotide diversity, significantly decreased with latitude similar to the expansion front. Also, we found that 89% of hermaphrodite individuals belong to one distinct in tree parsimony network haplotype. This frequency significantly decreased with latitude towards the expansion front. We suspect that the presence of hermaphrodites in trioecious populations may represent a trade-off between the possibility of producing progeny by single hermaphrodites and genetic variability loss through autogamy. S. myrsinifolia benefits from trioecious sexual systems under colonization events. This phenomenon is no longer a gain closer to the core of the species range.

Spatio-temporal dynamics of sex structure in trioecious and dioecious populations of Salix myrsinifolia

Most Salix species are characterized by a complex sex structure with populations that contain different ratios of male, female (dioecious populations) and even hermaphroditic individuals (trioecious populations). However, our knowledge of the temporal and spatial variability of such populations is rudimentary. I studied how sexual structure in trioecious populations of Salix myrsinifolia changes over time (from 1995 to 2012) and space in 32 populations across NE Poland and Lithuania. Additionally, the sex of marked individuals was monitored in a population over eight seasons. A number of land cover variables, latitude and population size were investigated to determine what possible mechanisms/factors affect the occurrence of hermaphroditism in this species. Sex structure was found to differ between the northern and southern parts of the study area (primary and secondary ranges), with trioecious populations occurring significantly more often in the secondary part of the range. Females dominated in northern dioecious populations, while sex ratios were balanced in the southern part of the range and in trioecious populations. The mean frequency of hermaphrodites reached 14 % and was decreasing toward the north. The sex structure remained stable over the study period, with an increasing frequency of hermaphrodites (by nearly 6 %). A detailed study of marked individuals revealed that sex is labile in this species. Over 12 % of individuals changed sex from one to three times. Most changes (67 %) were to hermaphroditism, which frequently occurred (34 %) just before death or when entering the post-reproductive period.

Hybridisation Dynamics between the Greater Spotted Eagles Aquila clanga and Lesser Spotted Eagles Aquila pomarina in the Biebrza River Valley (NE Poland)

Abstract. We studied a sympatric and crossbreeding population of the Lesser and the Greater Spotted Eagle in the Biebrza Valley, NE Poland. In order to follow the dynamics of hybridisation and its possible causes we monitored these two species between 1996 and 2012, using visual and genetic species identification. Individuals in up to 51 territories annually were determined as one of the two species or as a hybrid according to plumage characteristics. Feathers from adults and chicks from 114 broods were collected and genotyped using 30 nuclear markers. Hybridisation was observed with both methods already at the beginning of the study, and showed a significantly increasing trend. The proportion of broods producing hybrids of the Greater and the Lesser Spotted Eagle increased during the study by over 30%. The percentage of territories occupied by pure Greater Spotted Eagle pairs declined to 50% at the end of the study. The increasing number of mixed pairs highly significantly correlated with the decreasing number of pairs of the rare Greater Spotted Eagle, but weakly with the numbers of the more common Lesser Spotted Eagle. Mate replacement was frequently recorded and favoured the Lesser Spotted Eagle or hybrids. Adult males were the most often replaced sex (71%), possibly due to their higher mortality. Sex ratio at the nestling stage did not diverge from 1:1. Overall, 13 cases of within-pair species composition change were recorded, leading mostly to hybridisation (61%), but sometimes also to re-establishment of pure A. clanga pairs (23%). Alteration of habitat towards that preferred by the Lesser Spotted Eagle and differential sex-mortality are discussed as the most possible causes of the increasing crossbreeding rate.

From past to future: impact of climate change on range shifts and genetic diversity patterns of circumboreal plants

Climate change is projected to influence the genetic resources of plant species. Recent research has examined genetic diversity patterns under current climate conditions, with little attention to the future genetic consequences for species. In this study, we combined ecological niche modeling and population genetic approaches to project future changes in genetic diversity using plastid and nuclear DNA and reconstructed distribution patterns of three circumboreal plants (Chamaedaphne calyculata, Linnaea borealis ssp. borealis, and Pedicularis sceptrum-carolinum ssp. sceptrum-carolinum) in the last glacial maximum. We found that circumboreal plants could potentially lose their geographic ranges in the future (2070; 35–52% in RCP 4.5 (representative concentration pathways), 37–53% in RCP 6.0, and 56–69% in RCP 8.5), only slightly compensated by a predicted range gain of 18–33% (across the three RCPs). It is expected that future genetic diversity level could remain similar or lower than the present level. On the other hand, the homogeneity of the genetic background—a lack of admixture and domination of one gene pool in most populations of C. calyculata and L. borealis ssp. borealis—was predicted to become more pronounced in the future. Combining the paleoecological niche modeling and genetic data revealed, more precisely, the climate refugia for circumboreal plants in the Alps, central Asia, Beringia, and southern North America and the macrorefugia more restricted to the northern part of Eurasia and North America, reaching the arctic zone.

Genetic determination of migration strategies in large soaring birds: evidence from hybrid eagles

The relative contributions of genetic and social factors in shaping the living world are a crucial question in ecology. The annual migration of birds to their wintering grounds and back provides significant knowledge in this field of research. Migratory movements are predominantly genetically determined in passerine birds, while in large soaring birds, it is presumed that social (cultural) factors play the largest role. In this study, we show that genetic factors in soaring birds are more important than previously assumed. We used global positioning system (GPS)-telemetry to compare the autumn journeys and wintering ranges of two closely related large raptorial bird species, the greater spotted eagle Clanga clanga and the lesser spotted eagle Clanga pomarina, and hybrids between them. The timing of migration in hybrids was similar to that of one parental species, but the wintering distributions and home range sizes were similar to those of the other. Tracking data were supported by habitat suitability modelling, based on GPS fixes and ring recoveries. These results suggest a strong genetic influence on migration strategy via a trait-dependent dominance effect, although we cannot rule out the contribution of social interactions.