Combining ecological research with environmental education

The relationship between ecological research and environmental education prograllllleS at the Hazeva Field Study Centre in Israel is described. Mutual benefits to both researchers and students are discussed and the benefits to the environment outlined

Submaximal Oviposition Rates in a Mymarid Parasitoid: Choosiness Should Not Be Ignored

Cronin and Strong (1993a, b) examined the oviposition behavior of Anagarus delicatus Dozier (Hymenoptera: Mymaridae), an egg parasitoid of the leafhopper Prokelisia marginate Van Duzee (Homoptera: Delphacidae). They reported oviposition rates that were lower than predicted if the rate of egg-laying was maximized. Cronin and Strong (1993a) considered, and subsequently rejected, several “rules of thumb” (Stephens and Krebs 1986) as explanations for the observed patterns of patch departure. They observed that hosts on leaves experience density-independent mortality due to leaf senescence. Based on that, they advanced the hypothesis that submaximal oviposition rates in A. delicatus are best explained as risk-spreading by the parasitoid. (That is, by laying a small number of eggs on many leaves, the parasitoid increases the probability that some of her offspring will survive; Cronin and Strong 1993a.) An alternative hypothesis (Rosenheim and Mangel 1994) suggests that by distributing the eggs among several leaves, A. delicatus avoids self-superparasitism. Here, we take a somewhat different approach than those provided above to explain an additional observation of Cronin and Strong (1993a): female wasps rejected most of the hosts that they had probed. In so doing, we argue that rate maximization was an inappropriate prediction for A. delicatus, and in light of the life history parameters of this species, egg limitation is more suitable. Furthermore, egg limitation, when combined with one of the proposed explanations for the distribution of eggs, can explain the high rejection level of potential hosts

Submaximal Oviposition Rates in a Mymarid Parasitoid: Choosiness Should Not Be Ignored

Cronin and Strong (1993a, b) examined the oviposition behavior of Anagarus delicatus Dozier (Hymenoptera: Mymaridae), an egg parasitoid of the leafhopper Prokelisia marginate Van Duzee (Homoptera: Delphacidae). They reported oviposition rates that were lower than predicted if the rate of egg-laying was maximized. Cronin and Strong (1993a) considered, and subsequently rejected, several “rules of thumb” (Stephens and Krebs 1986) as explanations for the observed patterns of patch departure. They observed that hosts on leaves experience density-independent mortality due to leaf senescence. Based on that, they advanced the hypothesis that submaximal oviposition rates in A. delicatus are best explained as risk-spreading by the parasitoid. (That is, by laying a small number of eggs on many leaves, the parasitoid increases the probability that some of her offspring will survive; Cronin and Strong 1993a.) An alternative hypothesis (Rosenheim and Mangel 1994) suggests that by distributing the eggs among several leaves, A. delicatus avoids self-superparasitism. Here, we take a somewhat different approach than those provided above to explain an additional observation of Cronin and Strong (1993a): female wasps rejected most of the hosts that they had probed. In so doing, we argue that rate maximization was an inappropriate prediction for A. delicatus, and in light of the life history parameters of this species, egg limitation is more suitable. Furthermore, egg limitation, when combined with one of the proposed explanations for the distribution of eggs, can explain the high rejection level of potential hosts

Mitochondrial DNA Variation, but Not Nuclear DNA, Sharply Divides Morphologically Identical Chameleons along an Ancient Geographic Barrier

The Levant is an important migration bridge, harboring border-zones between Afrotropical and palearctic species. Accordingly, Chameleo chameleon, a common species throughout the Mediterranean basin, is morphologically divided in the southern Levant (Israel) into two subspecies, Chamaeleo chamaeleon recticrista (CCR) and C. c. musae (CCM). CCR mostly inhabits the Mediterranean climate (northern Israel), while CCM inhabits the sands of the north-western Negev Desert (southern Israel). AFLP analysis of 94 geographically well dispersed specimens indicated moderate genetic differentiation (PhiPT = 0.097), consistent with the classical division into the two subspecies, CCR and CCM. In contrast, sequence analysis of a 637 bp coding mitochondrial DNA (mtDNA) fragment revealed two distinct phylogenetic clusters which were not consistent with the morphological division: one mtDNA cluster consisted of CCR specimens collected in regions northern of the Jezreel Valley and another mtDNA cluster harboring specimens pertaining to both the CCR and CCM subspecies but collected southern of the Jezreel Valley. AMOVA indicated clear mtDNA differentiation between specimens collected northern and southern to the Jezreel Valley (PhiPT = 0.79), which was further supported by a very low coalescent-based estimate of effective migration rates. Whole chameleon mtDNA sequencing (∼17,400 bp) generated from 11 well dispersed geographic locations revealed 325 mutations sharply differentiating the two mtDNA clusters, suggesting a long allopatric history further supported by BEAST. This separation correlated temporally with the existence of an at least 1 million year old marine barrier at the Jezreel Valley exactly where the mtDNA clusters meet. We discuss possible involvement of gender-dependent life history differences in maintaining such mtDNA genetic differentiation and suggest that it reflects (ancient) local adaptation to mitochondrial-related traits

Life-history decisions under predation risk: Importance of a game perspective

We model ontogenetic shifts (e.g. in food or habitat use) during development under predation risk. We ask whether inclusion of state and frequency dependence will provide new insights when compared with game-free life-history theory. We model a simple biological scenario in which a prey animal must switch from a low-predation, low-growth habitat to a high-predation, high-growth habitat. To assess the importance of frequency dependence, we compare the results of four scenarios of increasing complexity: (1) no predation; (2) constant predation; (3) frequency-dependent predation (predation risk diluted at high prey density); and (4) frequency-dependent predation as in (3) but with predators allowed to respond adaptively to prey behavior. State dependence is included in all scenarios through initial size, assumed to be environmental. A genetic algorithm is used to search for optimal solutions to the scenarios. We find substantially different results in the four different scenarios and suggest a decision tree by which biological systems could be tested to ascertain which scenario is most applicable

Thermal conditions determine lizards’ response to oil contamination in a desert habitat

Summary: A unique, hyper-arid habitat in southern Israel was polluted by crude oil in 2014. Surveys following the event found that some species of local lizards avoid the oil, while other species were found more frequently in polluted plots. These results raised the question: why do species react differently to oil-polluted soil? We evaluated how soil type, thermal conditions, and food availability interacted to shape habitat preferences of three lizard species. Generally, thermal conditions determined habitat selection and preferences for contaminated or clean soils, while the effects of food availability were weak. The diurnal Acanthodactylus opheodurus avoided artificial heating sources, perhaps to avoid hot soil during warm hours. Both nocturnal Stenodactylus species showed a preference for higher temperature treatments. While crude oil is considered harmful, ectotherms may not recognize it as a danger and may be attracted to it due to its thermal properties, which may create an ecological trap

Limited kin discrimination abilities mediate tolerance toward relatives in polyembryonic parasitoid wasps.

We modeled the possible effect of limited kin discrimination on larval aggression in polyembryonic wasps. In these organisms, each egg divides clonally to produce several genetically identical embryos inside an arthropod host. If more than one egg is laid inside a host (superparasitism), several clones compete for the host resources. In some species, a proportion of embryos develop into sterile soldier larvae that attack competitors inside the host. Soldiers were shown to attack according to relatedness, with higher levels of aggression toward less related individuals. Yet, the tolerance of soldiers toward nonclonal relatives is puzzling, given the intense competition for host resources, which is not offset by inclusive fitness. Using a decision tree model, we looked for conditions that justify soldier tolerance. We assumed 2 possible strategies for a soldier: A tolerant soldier does not attack a competing clone and an aggressive soldier attacks any clone that it identifies as a competitor. We calculated the expected payoffs of each strategy under different conditions of relatedness and probabilities for discrimination errors. The model predicts that when discrimination ability is perfect, a soldier should attack any competitor, regardless of relatedness. However, when discrimination ability is restricted, soldiers should switch from aggression to tolerance with increasing relatedness to competitors. The model demonstrates that limited discrimination abilities may shift the threshold of relatedness required to induce tolerance. This may apply to other systems of kin recognition that are prone to discrimination errors