Göran Nilson

Reproductive Tactics in an Island Population of Adders, Vipera berus (L.), with a fluctuating Food Resource

This paper describes the density fluctuations of the adder Vipera berus and its prey during seven years. The reproduction during high adder density and low food availability was compared with that seven years later in the same population during low adder density and high food availability. Female length was similar but weight status (mass/length 2.56 ) was significantly higher during high prey density. Female mass loss when giving birth and clutch mass were significantly higher during high availability of food, but relative clutch mass and relative mass loss were similar in the two situations. However, the variance in relative clutch mass was significantly lower with high prey density. Clutch size and mass per young were significantly higher during high prey density. During high food availability there were significant positive correlations between female length (~ age) and birth mass loss, female length and clutch mass, female length and clutch size, clutch mass and mass per young and between relative clutch mass and mass per young. During low food availability there were significant positive correlations between clutch mass and clutch size and relative clutch mass and clutch size. A significant negative correlation was found between female length and relative mass loss. This study do not conform entirely to general theories on reproductive adaptations to varying food availability (r-K strategies). During high prey density both more and heavier young were produced than during scarcity of food. A high correlation of reproductive parameters during high food availability indicates a maximal utilization of reproductive capacity in most females, while the lack of such correlations during low food availability indicates a varying access to food and fat storage possibility among females.

Reproductive success and risk of predation in normal and melanistic colour morphs of the adder, Vipera berus

In a population of adders (Vipera berus) in Southwest Sweden, melanistic males were heavier than normal coloured males of the same length. Victory in male-male sexual combats was positively related to size. Higher risk of predation in the black morph was inferred from experiments showing a high predator attack rate on models of the black morph. Even the bright colour in newly moulted basking males of the normal morph gives cryptic protection. In females, melanism probably also affects body size and risk of predation by visually searching predators. The thermoregulatory influence of black colour, the reproductive success and the maintenance of two colour morphs in the population are discussed.

Tolerance to low pH in a population of moor frogs, Rana arvalis, from an acid and a neutral environment: a possible case of rapid evolutionary response to acidification

A possible evolutionary process towards increased adaptation to acid conditions was examined in a population of moor frogs, Rana arvalis Nilsson, exposed to critically low pH levels for approximately 15 generations. Rana arvalis eggs from the acid locality studied were not significantly larger than those from a neutral locality, but egg size variation was significantly smaller. No embryonic or early larval survival variables were correlated with egg size, and neither size at, nor time to metamorphosis was correlated with egg size. In acid water, embryonic and larval survival variables were all significantly higher in progeny from the acid locality, and larvae from this population metamorphosed earlier and at a larger size than larvae originating from a neutral locality. All premetamorphic stages of Rana arvalis from the acid locality had a higher acid tolerance than the population from a neutral environment. Thus, an adaptation to acid conditions may have taken place in the moor frog population exposed to increasingly low pH breeding water during a period of 30 to 40 yr. Limb deformations at low pH and high growth rate could not be verified in froglets of this species.

Function of renal sex secretion and male hierarchy in the adder, Vipera berus, during reproduction

Abstract The function of the male renal sex segment secretions in the adder, Vipera berus, was studied. Renal sex segments in male adders were hypertrophied immediately before and during the mating period. Simultaneously, renal secretion was found in the entire ureter and coprodeum. Newly mated females have long, slightly convoluted, and hard posterior uteri, while females prior to mating, and nonreproductive ones, have weakly contracted or flaccid uteri. Uteri in newly mated females had a contracted sphincter muscle with reduced and compressed folded lumen. Uteri in an estrous female supplied with vital stained renal secretion became hard posteriorly. The stained secretion reached the entrance of the uteri, where the hard parts started. Estrous females artificially supplied with male sex secretion showed a significant decrease in acceptance of male courtship. Administration of renal sex secretion also interfered with reproduction.

Ovarian cycle and reproductive dynamics in the female adder, Vipera berus (Reptilia, Viperidae)

Studies of reproductive organs, fat body and liver in relation to different activity periods were made to describe the breeding biology of the female adder, Vipera berus, in SW Sweden. The female adder is a biennial breeder. Vitellogenesis and formation of preovulatory follicles start in autumn the non-reproductive year and continue to the end of May the following spring when ovulation takes place. Copulation precedes ovulation and sperm is found in uterus a month before ovulation. Primary oocytes were seen after ovulation in the reproductive year. Atresia were seen more frequently during reproductive years and in all classes of follicles. Clutch size (X=8.8) had a linear increase with female body size and juveniles were born in early August. Thecal gland cells increased in number and the epithelium of the uterus became hypertrophied late in the non-reproductive year and early in the reproductive year. The weight of the ovary, fat body and liver went through a cyclic pattern with the highest peak in the reproductive spring. Fat body and liver weights were lowest at the end of the gestation period. Feeding periods, fat mobilization, reproductive effort, endocrine ectivity and adaptive value of the biennial reproduction are discussed. The adaptation to short season habitats is stressed.

Strike-induced chemosensory searching in Old World vipers and New World pit vipers

It is known that striking rodent prey induces a sustained, high rate of tongue flicking in rattlesnakes. The present study shows this phenomenon (called strike-induced chemosensory searching, SICS) to occur in species of rattlesnakes not previously investigated and in two species ofAgkistrodon. SICS occurs in Old World vipers (Eristocophis, Vipera, Bitis), including species which normally hold their prey after striking. A hypothesis is offered which (1) accounts for the occurrence of SICS in these latter species and (2) suggests that SICS in some viperids may have arisen through paedomorphic evolution. More generally, it is concluded that SICS is probably a homologous trait in vipers and pit vipers and that the trait may have first appeared in elapid ancestors of the viperidae.

Phylogeny and systematics of viperine snakes. III: resurrection of the genus Macrovipera (Reuss, 1927) as suggested by biochemical evidence

The phylogenetic relationships of the large Palaearctic vipers (Daboia sensu Obst, 1983) and Eristicophis were investigated using immunological comparisons of blood serum albumin and blood serum electrophoresis. The genus Echis was used for outgroup comparisons. Daboia was found to be polyphyletic. The name Daboia should be restricted to the type species russelli which was found to have the same immunological distance to the lebetina group as the monophyletic Pseudocerastes-Eristicophis group. The lebetina group was found to consist of the four species lebetina, schweizeri, mauritanica and deserti. For this group the generic name Macrovipera is revalidated. The taxa schweizeri and deserti are treated as full species. Vipera palaestinae was found to be the closest relative of the V. xanthina group. Nomenclatural history and distribution of the involved taxa is reviewed. Descriptions and diagnoses for the genus Macrovipera and the included species are given.

Breeding pool characteristics and reproduction in an island population of natterjack toads, Bufo calamita Laur., at the Swedish west coast

A group of isolated populations of the natterjack toad, Bufo calamita Laur., occur on small and rocky islands in the outer archipelago at the Swedish west coast. Breeding pool characteristics were studied in one of these populations. Egg strings were deposited in 31 of 95 possible rock pools from mid May to mid August. Significant correlations were found between breeding and 1) pool size, 2) pool water depth, 3) shore line inclination, 4) height of pool above sea level, and 5) distance to nearest sea shore line. The breeding pool selected may be a compromise between highest possible water temperature and the risk that a shallow pool dries up before metamorphoses.

Mitochondrial phylogeny shows multiple independent ecological transitions and northern dispersion despite of Pleistocene glaciations in meadow and steppe vipers (Vipera ursinii and Vipera renardi)

The phylogeny and historical demography of small Eurasian vipers of the Vipera ursinii and V. renardi complexes were studied using mitochondrial DNA sequences analysed with Bayesian inference, Maximum Likelihood and Maximum Parsimony approaches, and mismatch distributions. Diversification in the group resulted from an initial dispersion in the later Pliocene - Pleistocene in two directions: north-westwards via the Balkans (V. ursinii complex) and north-eastwards from Asia Minor via the Caucasus (V. renardi complex). An independent, comparatively recent transition occurred from montane habitats to lowland grasslands in different mitochondrial lineages during the Late Pleistocene, when representatives of the both complexes had reached lowland steppes to the north. Effective population size showed clear signs of rapid growth in eastern V. renardi, triggered by colonization of vast lowland steppes, but in western V. ursinii complex grew during the Last Glaciation and experienced stabilization in Holocene. Expansion and population growth in lowland lineages of V. renardi was not strongly affected by Pleistocene climatic oscillations, when cold, dry conditions could have favoured species living in open grasslands. The high diversity of closely related haplotypes in the Caucasus and Tien-Shan could have resulted from repetitive expansion-constriction-isolation events in montane regions during Pleistocene climate fluctuations. The mitochondrial phylogeny pattern conflicts with the current taxonomy.

A re-evaluation of the taxonomic status of the Moldavian steppe viper based on immunological investigations, with a discussion of the hypothesis of secondary intergradation between Vipera ursinii rakosiensis and Vipera (ursinii) renardi

The taxonomic level and phylogenetic relationship of the Moldavian steppe viper was investigated using blood serum electrophoresis, immunological comparisons of blood serum albumin and morphological comparisons. The traditional hypothesis that the Moldavian steppe viper is a secondary intergradation between Vipera (ursinii) renardi and V. ursinii rakosiensis could not be verified. Although morphologically similar (but not identical) to these two taxa, it has a closer immunological distance to the Balkan mountain subspecies, V. u. macrops and V. u. graeca. Specific antisera against serum albumins of V. u. graeca, V. u. ursinii (wettsteini) and V. u. eriwanensis were available, and the three vipers to be tested: rakosiensis, renardi and the Moldavian steppe viper branch off from different stems: rakosiensis seems close to ursinii, V. (u.) renardi appears fairly close to eriwanensis, both of which share a common stem with the rakosiensis-ursinii lineage. The Moldavian steppe viper shows high distance to both ursinii and eriwanensis, but low distance to graeca. The electrophoretic pattern show great differences from all other geographic forms tested (seven). We conclude that the Moldavian steppe viper represents a separate subspecies: Vipera ursinii moldavica ssp.n.