The orchid family is renowned for its enormous diversity of pollination mechanisms and unusually high occurrence of non-rewarding flowers compared to other plant families. The mechanisms of deception in orchids include generalized food deception, food-deceptive floral mimicry, brood-site imitation, shelter imitation, pseudoantagonism, rendezvous attraction and sexual deception. Generalized food deception is the most common mechanism (reported in 38 genera) followed by sexual deception (18 genera). Floral deception in orchids has been intensively studied since Darwin, but the evolution of non-rewarding flowers still presents a major puzzle for evolutionary biology. The two principal hypotheses as to how deception could increase fitness in plants are (i) reallocation of resources associated with reward production to flowering and seed production, and (ii) higher levels of cross-pollination due to pollinators visiting fewer flowers on non-rewarding plants, resulting in more outcrossed progeny and more efficient pollen export. Biologists have also tried to explain why deception is overrepresented in the orchid family. These explanations include: (i) efficient removal and deposition of pollinaria from orchid flowers in a single pollinator visit, thus obviating the need for rewards to entice multiple visits from pollinators; (ii) efficient transport of orchid pollen, thus requiring less reward-induced pollinator constancy; (iii) low-density populations in many orchids, thus limiting the learning of associations of floral phenotypes and rewards by pollinators; (iv) packaging of pollen in pollinaria with limited carry-over from flower to flower, thus increasing the risks of geitonogamous self-pollination when pollinators visit many flowers on rewarding plants. All of these general and orchid-specific hypotheses are difficult to reconcile with the well-established pattern for rewardlessness to result in low pollinator visitation rates and consequently low levels of fruit production. Arguments that deception evolves because rewards are costly are particularly problematic in that small amounts of nectar are unlikely to have a significant effect on the energy budget of orchids, and because reproduction in orchids is often severely pollen-, rather than resource-limited. Several recent experimental studies have shown that deception promotes cross-pollination, but it remains unknown whether actual outcrossing rates are generally higher in deceptive orchids. Our review of the literature shows that there is currently no evidence that deceptive orchids carry higher levels of genetic load (an indirect measure of outcrossing rate) than their rewarding counterparts. Cross-pollination does, however, result in dramatic increases in seed quality in almost all orchids and has the potential to increase pollen export (by reducing pollen discounting). We suggest that floral deception is particularly beneficial, because of its promotion of outcrossing, when pollinators are abundant, but that when pollinators are consistently rare, selection ...

One of the central problems in contemporary ecology and conservation biology is the drastic change of landscapes induced by anthropogenic activities, resulting in habitat loss and fragmentation. For many wild living species, local extinctions of fragmented populations are common and recolonization is critical for regional survival. Successful recolonization depends on the availability of dispersing individuals and the degree of landscape connectivity. The obvious implications of landscape connectivity for conservation biology have led to a proliferation of connectivity measures. However, general relationships between landscape connectivity and landscape structure are lacking, and so are the relationships between different connectivity metrics. Consequently, there is a need to develop landscape metrics that more accurately characterize the landscape with an emphasis on the underlying processes. Here we review various definitions of landscape connectivity, explain their mathematical connotations, and make some unifying conclusions and suggestions for future research.

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The best strategy for an organism to deal with unpredictable environmental conditions is a stochastic one, but it is not easy to distinguish it from nonadaptive randomness in phenotype production, and its convincing demonstrations are lacking. Here we describe a new method for detection of adaptive stochastic polyphenism and apply it to the following problem. In fall, each female of the bird cherry-oat aphid, Rhopalosiphum padi, faces a decision either to produce sexuals, which mate and lay cold-tolerant eggs, or to continue production of cold-sensitive parthenogenetic females, which potentially yields a higher population growth rate but is risky because a cold winter can kill all of her descendants. Using a simulation model, we show that global investment in sexual reproduction should be proportional to winter severity and that variance in the peak date of production of sexual individuals should depend on climate predictability. Both predictions are validated against standardized trap data on aphid flight accompanied by meteorological data, and the predictions support adaptive phenotypic plasticity.

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We investigated the response of four species of aphids (Metopeurum fuscoviride, Brachycaudus cardui, Aphis fabae, and Macrosiphoniella tanacetaria) on tansy (Tanacetum vulgare) to plant quality and attendance by an ant, Lasius niger. The aphids experienced one of four different environments for two consecutive generations. Ant‐attendance significantly affected the time needed to reach maximum fecundity only in Me. fuscoviride and plant quality in Me. fuscoviride and B. cardui. Maximum daily fecundity was positively affected by plant quality and the magnitude of the effect was inversely associated with the degree of myrmecophily. Ant‐attendance had a positive effect on maximum fecundity only in the obligate myrmecophile, Me. fuscoviride. The intrinsic rate of population increase, rm, on high quality plants, was lowest for the obligate myrmecophile, intermediate for the facultative myrmecophiles and highest for the unattended species. On high quality plants the fitness of Me. fuscoviride was more adversely affected by the developmental stage of the plant and absence of ants than that of A. fabae or Ma. tanacetaria, which were able to maintain a high relative fitness in all the environments. The implications for aphids experiencing different degrees of ant‐attendance and seasonal changes in plant quality are discussed.