Szilvia Kövér

Restricted within-habitat movement and time-constrained egg laying of female Maculinea rebeli butterflies

The movement of butterflies within habitat patches is usually assumed to be random, although few studies have shown this unambiguously. In the case of the highly specialized genus Maculinea, two contradictory hypotheses exist to explain the movement and distribution of imagos within patches: (1) due to the high spatial variance of survival rates among caterpillars, the “risk-spreading” hypothesis predicts that females will tend to make linear flight paths in order to maximize their net displacement and scatter the eggs as widely as possible; and (2) recent mark–release–recapture (MRR) data suggest that within-habitat displacement of some Maculinea species is constrained and that adults may establish home ranges. We tested both hypothesis by analysing the movement pattern of individuals. We also investigated whether egg laying is time constrained, which would enhance the trade-off between flying and egg laying. Thirty females of Maculinea rebeli (Lepidoptera: Lycaenidae) were tracked within a single population in Central Hungary. Their egg-laying behaviour and individual patterns of movement were recorded, and the latter were compared with random walk model predictions. The population was also sampled by MRR to estimate survival rates, and four non-mated, freshly eclosed females were dissected to assess their potential egg load. Net squared displacement of females was significantly lower than predicted by the random walk model and declined continuously after the 15th move. The ratio of net displacement and cumulative move length decreased with the number of moves, supporting the hypothesis that Maculinea butterflies establish home ranges. We found that low survival and a low rate of egg laying prevented females from laying their potential number of eggs within their lifespan. Time limitation increased the cost of movement, providing another possible explanation for the restricted movement of females.

Species-specific distribution of two sympatric Maculinea butterflies across different meadow edges

An important consequence of habitat fragmentation is the increase of edge habitats. Environmental factors in the edges are different from those in the interiors, which causes changes in the distribution of plant and animal species. We aimed to study how edges affect the distribution of two butterfly species within meadow fragments. We therefore investigated the effect of distance from edge and edge type (road edge versus tree edge) on two sympatric large blue species (Maculinea teleius and M. nausithous). Our results showed that edge type had contrasting effects on the two species. M. teleius favoured both interiors and road edges, while M. nausithous preferred the tree edges. In the case of the latter species a strong positive edge effect was also found. This kind of within-habitat niche segregation is probably related to the different microenvironmental conditions at the edges. Foodplant density did not seem to limit the distribution of these species. Our results suggest that interiors of meadows are important for M. teleius, while tree edges maintain the habitats of the regionally rarer butterfly, M. nausithous.

The effects of genetic relatedness on mate choice and territorial intrusions in a monogamous raptor

AbstractKin recognition has been shown in some bird species, suggesting that birds might be able to actively avoid inbreeding through mate choice. However, the evidence for such behaviour in wild bird populations is scarce. Intrusions performed by conspecifics could be part of the breeding strategy of a territorial bird species: an intruder might find the opportunity to replace a resident individual and acquire its territory. If intruders seek the opportunity to breed, their relatedness to the opposite-sex resident could influence their nest site intrusions similarly to mate choice. Observations of intrusions also revealed that vagrant juveniles of long-lived raptors repeatedly visit their natal population before maturation. The present study focused on the White-tailed Eagle (Haliaeetus albicilla): a territorial, long-lived, monogamous raptor species. We investigated whether (1) relatedness is considered in mate choice in this species, based on noninvasively collected DNA samples. (2) We furthermore addressed whether nest site intrusions could be explained by any of the following three nonexclusive hypotheses: (i) finding a mate, (ii) acquiring a good-quality territory, or (iii) visiting the natal area. Our results suggest that White-tailed Eagles avoid kin in mate choice. Although a considerable proportion of the intruders were juveniles, none of them was likely to be offspring of resident pairs of the study population. We found a nonsignificant trend towards lower relatedness than expected from random intrusions in both sexes. The revealed intrusion events suggest a sex bias: males seem to prefer better-quality territories more than females do.ZusammenfassungEffekte der genetischen Verwandtschaft auf die Partnerwahl und auf territoriales Eindringen bei einem monogamen Greifvogel Verwandtenerkennung ist bei einigen Vogelarten nachgewiesen, was darauf hindeutet, dass Vögel fähig, sind Inzucht durch Partnerwahl aktiv zu verhindern. Dennoch verfügen wir nur über vereinzelte Beweise für solch ein Verhalten in wildlebenden Populationen. Eindringen auf das Territorium von Artengenossen kann als Teil der Paarungsstrategie von territorialen Vögeln funktionieren: der Eindringling kann dadurch das ansässige Tier ersetzen und sein Territorium übernehmen. Falls Eindringlinge Paarungsgelegenheiten suchen, kann ihre Verwandtschaft mit den Residenten des anderen Geschlechts die Eindringungen am Neststandort ähnlich wie bei der Partnerwahl beeinflussen. Beobachtungen haben auch gezeigt, dass umherstreifende Jungtiere langlebiger Greifvögel vor der Geschlechtsreife ihre Geburtspopulation wiederholt aufsuchen. Wir gingen dieser Frage am Seeadler (Haliaeetus albicilla) nach, einer territorialen, langlebigen, monogamen Greifvogelart. Erstens untersuchten wir mittels nichtinvasiv-gesammelten DNS Proben, ob Verwandtschaft in der Partnerwahl bei dieser Art berücksichtigt wird. Zusätzlich haben geprüft, ob Eindringungen am Neststandort erklärt werden können durch (i) Partnersuche, (ii) Erlangung eines Territoriums von guter Qualität, oder (iii) Aufsuchen der Geburtsgebietes. Unsere Ergebnisse weisen darauf hin, dass Seeadler ihre nahen Verwandten während der Partnerwahl vermeiden. Obwohl eine beträchtlicher Anteil der Eindringlinge Jungtiere waren, waren diese wahrscheinlich nicht der Nachwuchs der residenten Paare. Wir fanden eine nicht signifikante Tendenz zu niedrigerer Verwandtschaft als bei zufälligen Eindringungen der beiden Geschlechter zu erwarten wäre. Die aufgedeckten Eindringungsereignisse deuten auf einen Unterschied zwischen den Geschlechtern hin: Männchen schienen Territorien von besserer Qualität mehr zu bevorzugen als Weibchen.