Age‐dependent plasticity in reproductive investment, regeneration capacity and survival in a partially clonal animal (Hydra oligactis)

Asexual reproduction diversifies life‐history priorities and is associated with unusual reproduction and somatic maintenance patterns, such as constant fertility with age, extensive regeneration ability and negligible senescence. While age‐dependent plasticity in relative allocation to sexual versus asexual reproductive modes is relatively well studied, the modulation of somatic maintenance traits in parallel with age‐dependent reproduction is much less well understood in clonal or partially clonal animals. Here, we asked how age‐dependent investment into sexual and asexual reproduction co‐varies with somatic maintenance such as regeneration in a partially clonal freshwater cnidarian Hydra oligactis, a species with remarkable regeneration abilities and experimentally inducible sex. We induced gametogenesis by lowering temperature at two ages, 1 or 4 weeks after detachment from an asexual parent, in animals of a male and a female clone. Then we measured phenotypically asexual and sexual reproductive traits (budding rate, start day and number of sexual organs) together with head regeneration rate, survival and the cellular background of these traits (number of reproductive and interstitial stem cells) for 2 or 5 months. Younger animals had higher asexual reproduction while individuals in the older group had more intensive gametogenesis and reproductive cell production. In parallel with these age‐dependent reproductive differences, somatic maintenance of older individuals was also impacted: head regeneration, survival and interstitial stem cell numbers were reduced compared to younger polyps. Some of the traits investigated showed an ontogenetic effect, suggesting that age‐dependent plasticity and a fixed ontogenetic response might both contribute to differences between age groups. We show that in H. oligactis asexual reproduction coupled with higher somatic maintenance is prioritized earlier in life, while sexual reproduction with higher maintenance costs occurs later if sex is induced. These findings confirm general life‐history theory predictions on resource allocation between somatic maintenance and sexual reproduction applying in a partially clonal species. At the same time, our study also highlights the age‐dependent integration of these resource allocation decisions with sexual/asexual strategies. Accounting for age‐related differences might enhance repeatability of research done with clonal individuals derived from mass cultures

The evolution of parental cooperation in birds

Parental care is one of the most variable social behaviors and it is an excellent model system to understand cooperation between unrelated individuals. Three major hypotheses have been proposed to explain the extent of parental cooperation: sexual selection, social environment, and environmental harshness. Using the most comprehensive dataset on parental care that includes 659 bird species from 113 families covering both uniparental and biparental taxa, we show that the degree of parental cooperation is associated with both sexual selection and social environment. Consistent with recent theoretical models parental cooperation decreases with the intensity of sexual selection and with skewed adult sex ratios. These effects are additive and robust to the influence of life-history variables. However, parental cooperation is unrelated to environmental factors (measured at the scale of whole species ranges) as indicated by a lack of consistent relationship with ambient temperature, rainfall or their fluctuations within and between years. These results highlight the significance of social effects for parental cooperation and suggest that several parental strategies may coexist in a given set of ambient environment

Roadside verges as habitats for endangered lizard-orchids (Himantoglossum spp.): Ecological traps or refuges?

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Distribution and seed production of the rare, dry grassland specialist Sternbergia colchiciflora (Amaryllidaceae) in Pannonian cemeteries

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Turkish graveyards as refuges for orchids against tuber harvest

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Biological flora of Central Europe Himantoglossum adriaticum H. Baumann

Himantoglossum adriaticum H. Baumann is a long-lived perennial orchid with an adriato-mediterranean distribution. The species-level separation of this species from the more geographically widespread H. hircinum has only recently been confirmed via a combination of molecular and morphometric techniques, which are further developed here. To provide a comprehensive overview of its autecology we integrated previously published information with extensive unpublished data derived mainly from populations in the Keszthely Hills of Hungary. In this paper we assess the distribution, habitat preferences, life history and seed germination (ex situ and in situ) of H. adriaticum, with special emphasis on its reproductive biology