Włodzimierz Chętnicki

Genetic differentiation of polish populations of Sorex araneus L. III : Interchromosomal recombination in a hybrid zone

Two parapatric chromosomal races of the common shrew (Sorex araneus) in Poland differ in their complement of metacentric arm combinations: hk, io, gr, nm (race IV), and hi, ko, gm, np (race II). In hybrids, these eight race‐diagnostic metacentrics form two randomly segregating complexes. The first complex (C1) occurs in the form of a ring configuration ok/kh/hi/io, or a chain o/ok/kh/hi/i (when there is Robertsonian polymorphism of the element io). The second complex (C2) always takes the form of a six‐element chain configuration r/rg/gm/mn/np/p. The C2 complex may be shortened to five or even four elements, when acrocentrics g, m and n are present. In the contact zone we found shrews of pure races (race II or IV), as well as hybrids with C1 or C2 complexes, and recombinants hi, ko, gr, nm. Complex heterozygotes are likely to suffer reduced fertility due to malsegregation at meiosis. However, the C1 hybrids with ring configurations occur with a high frequency throughout the contact zone. This suggest that their fitness is only slightly lowered relative to pure race individuals, in contrast to the hybrids with C1 or C2 chain configurations, which presumably have a more heavily reduced fertility. On the other hand, at the center of the zone there is a high proportion of recombinants, which, being chromosomal homozygotes, should display normal meiotic segregation. Furthermore, the high frequencies of recombinants within the contact zone should facilitate gene flow between the races. The occurrence of recombinants plays a similar role as the appearance of the maximum frequencies of acrocentric homozygotes described in several contact zones of S. araneus.

Meiotic studies of male common shrews (Sorex araneus L.) from a hybrid zone between chromosome races

Thirty-three adult male common shrews (Sorex araneus L.) were collected from a hybrid zone between two chromosomal races that differed in Robertsonian metacentrics. Anaphase I nondisjunction frequencies were estimated on the basis of metaphase II counts. RIV and CV complex heterozygotes (four-element rings and five-element chains at meiosis I, respectively) had substantially higher nondisjunction rates than homozygotes and simple Robertsonian heterozygotes. However, at least in the case of RIV-forming hybrids, increased nondisjunction frequency did not result from malsegregation of the heterozygous complex. Extra elements found in hyperploid spreads were most frequently acrocentrics, that could not originate from a fully metacentric multivalent. Complex heterozygotes were also characterized by higher frequencies of univalents observed at diakinesis I. However, univalents did not originate from complex configurations, which were regularly formed with usually one chiasma per chromosome arm. Hence, we suppose that the presence of multivalents in the cell affects pairing and segregation of other elements at meiosis I.

Whole-arm reciprocal translocation in a hybrid population of Sorex araneus

A whole-arm reciprocal translocation (WART) between the metacentric chromosomes af and hk is described for a single hybrid between chromosome races Drnholec and Łęgucki Młyn. This translocation resulted in the metacentric chromosomes ah and fk, previously unknown in Sorex araneus. This study provides a description of an unambiguous case of a WART in S. araneus, a phenomenon that has recently been suggested to play a significant role in generating of chromosome races in this species.

Non-disjunction frequency in male complex Robertsonian heterozygotes of the common shrew

Common shrews display two types of Robertsonian (Rb) heterozygosity: simple (where CIII configurations are formed at meiosis I) and complex (which have longer meiotic chains or rings). Based on an analysis of large sample sizes (over 100) of MII cells per specimen, we estimated the non-disjunction frequency in seven Rb homozygotes and 21 complex Rb heterozygotes (CIV and CV) of Sorex araneus Linnaeus, 1758. The analysis showed high betweenindividual variability. The mean level of non-disjunction in homozygotes (2.01%) was significantly lower than in CIV and CV heterozygotes (4.27% and 5.78%, respectively). The study demonstrated that non-disjunction frequency in male CIV and CV heterozygotes was similar to that in simple heterozygotes in the common shrew.

Invalidation of Stobnica chromosome race of the common shrew Sorex araneus

In Central Poland, two similar chromosome races of the common shrewSorex araneus Linnaeus, 1758 were earlier described: Drnholec race (arm combinationsgm, hi, ko, nr) and Stobnica race (gm, hi, ko, np). Great similarity in size and G-banding patterns between thenr andnp metacentrics leave open to doubt the actual existence of both races in Poland. The present study, which is based on good quality karyotypes of common shrews from 18 sites, showed the presence of thenr arm combination. There is therefore strong evidence that thenp arm combination was wrongly described and thus the Stobnica race should not be considered valid.

Facultative Interspecific Brood Parasitism in Colonial Breeding Waterbirds in Biebrza National Park, Poland

Abstract. Interspecific brood parasitism occurs when the eggs of one species are laid in the nest of a different species, but evidence of this phenomenon is scarce. Facultative interspecific brood parasitism has been described in Charadriiformes. However, to our knowledge, our study provides the first documentation of facultative interspecific brood parasitism in the colonially breeding species we studied. The factors affecting its frequency in relation to colony species composition, nest density, and period of the breeding season was analyzed. Between 2006 and 2012, we monitored 2,493 nests of five species: Northern Lapwing (Vanellus vanellus; n = 745), Common Redshank (Tringa totanus; n = 467), Black-tailed Godwit (Limosa limosa; n = 237), Black-headed Gull (Chroicocephalus ridibundus; n = 932) and Common Tern (Sterna hirundo; n = 112). Facultative interspecific brood parasitism was observed in 1.3% of all nests. Typically, a single egg was laid in a host nest (59.4% of parasitized nests), and a maximum of four parasitic eggs were laid (3.1% of parasitized nests). The Common Redshank showed the highest frequency of facultative interspecific brood parasitism (59.4%), followed by Northern Lapwing (28.1%). Facultative interspecific brood parasitism occurred most frequently at the beginning of the breeding season (62.5% between the end of April and 10 May), although the number of active nests peaked later than did the number of parasitized nests. Hatching success of broods containing parasitic eggs was 17.8%, which was lower than that of non-parasitized nests (23.1%). Interspecific brood parasitism may evolve from conspecific brood parasitism in colonies with high nest densities. Low, but constant frequencies of facultative interspecific brood parasitism may suggest either that this is a strategy to increase fecundity or non-adaptive behavior derived from failures to identify the nest due to the high nest density in the colony.

Conspecific Brood Parasitism is Biased Towards Relatives in the Common Black-Headed Gull

Given the many detailed studies on the breeding biology of gulls, surprisingly little is known about conspecific brood parasitism (CBP) in these birds. CBP has been recorded in only a few of the roughly 60 species of Laridae. We studied CBP in two colonies of Common Black-headed Gull Croicocephalus ridibundus in northeastern Poland, during two consecutive years. We found parasitism in 22% and 10% of the monitored nests in the colonies, as determined with protein fingerprinting. Among the parasitic females we found only one that acted as both parasite and host. In both colonies, most cases of parasitism involved nests of females more related than average to the parasitic female. The rare cases of egg expulsion involved hosts with low relatedness to the parasite. We suggest that kin selection is implicated in CBP in the Blackheaded Gull.

Cases of coat colour anomalies in the common shrew, Sorex araneus L

Coat colour anomalies in the common shrew, Sorex araneus L., in the geographical range of this species, including Poland, are extremely rare. This study describes atypically coloured common shrews. Light colouration of the coat is a result of lack ofpigment in the entire hair or hair fragments. It appears that atypically coloured shrews occur more often in isolated populations whose gene transfer with neighboring populations is limited.

Sex Chromosome Meiotic Drive in Hybrid Males of the Common Shrew (Sorex araneus)

Patterns of sex chromosome segregation in six homozygous males of the common shrew (Sorex araneus LINNAEUS, 1758) belonging to two chromosomal races, as well as in 16 interracial hybrids were studied. Based on their karyotypes the hybrids can be subdivided into two groups: (a) complex heterozygotes, which form meiotic quadrivalents in chain and chain + ring configurations, and (b) complex heterozygotes, which form meiotic pentavalents in chain configurations. Random (1:1) segregation of sex chromosomes was found in homozygous as well as those heterozygous males which form meiotic complexes of four chromosomes. However, in some hybrids with meiotic pentavalents we observed a strong preferential segregation in favour of X chromosomes.

Chromosome polymorphism in Polish populations of northern birch mouse Sicista betulina1

Abstract. Somatic chromosomes of 17 northern birch mice, Sicista betulina, originating from lowland and Tatra Mountain populations were studied. In the whole studied material constant diploid number of chromosomes (2n = 32) was found. Polymorphism of a pair of large-sized autosomes was found; acrocentric, subtelocentric and submetacentric chromosomes in homozygous or heterozygous state form the polymorphic pair. Consequently, chromosome arm number (NF) varies within 60 and 62. In this regard Polish populations of northern birch mouse differ from those of more eastward distribution (NF = 63–64).