Predators marked with chemical cues from one prey have increased attack success on another prey species

1. To reduce the risk of being eaten by predators, prey alter their morphology or behaviour. This response can be tuned to the current danger if chemical or other cues associated with predators inform the prey about the risks involved. 2. It is well known that various prey species discriminate between chemical cues from predators that fed on conspecific prey and those that fed on heterospecific prey, and react stronger to the first. It is therefore expected that generalist predators are more successful in capturing a given prey species when they are contaminated with chemical cues from another prey species instead of cues from the same prey species. 3. Here, a generalist predatory mite was studied that feeds on thrips larvae as well as on whitefly eggs and crawlers. Mites were marked with cues (i.e. body fluids) of one of these two prey species and were subsequently offered thrips larva. 4. Predators marked with thrips cues killed significantly fewer thrips than predators marked with whitefly cues, even though the predator's tendency to attack was the same. In addition, more thrips larvae sought refuge in the presence of a predatory mite marked with thrips cues instead of whitefly cues. 5. This suggests that generalist predators may experience improved attack success when switching prey species.     

The nutrition of animal tissues cultivated in vitro. III. Use of a depletion technique for determining specific nutritional requirements

1. Cultivation of freshly explanted chick embryonic heart tissues in Hanks's salt solution for 3 to 4 days has been shown to create a general state of nutritional deficiency in the cultures. Provided the depletion is not prolonged beyond 4 days, the cultures subsequently revive and survive to a normal period in synthetic medium M 150. 2. Paper chromatographic studies on the culture medium have shown that the amino acid metabolism of the depleted cultures is restored to a normal pattern within a few days in medium M 150. 3. By the use of the nutritional deficiency technique, a coenzyme A requirement for this type of culture has been established. 4. The application of these findings to tissue cell nutrition and the possible hazards of using serum, or other uncharacterized additions, either to establish cultures, or as part of the experimental medium, are discussed.     

Concordant phylogeography and cryptic speciation in two Western Palaearctic oak gall parasitoid species complexes

Little is known about the evolutionary history of most complex multi‐trophic insect communities. Widespread species from different trophic levels might evolve in parallel, showing similar spatial patterns and either congruent temporal patterns (Contemporary Host‐tracking) or later divergence in higher trophic levels (Delayed Host‐tracking). Alternatively, host shifts by natural enemies among communities centred on different host resources could disrupt any common community phylogeographic pattern. We examined these alternative models using two Megastigmus parasitoid morphospecies associated with oak cynipid galls sampled throughout their Western Palaearctic distributions. Based on existing host cynipid data, a parallel evolution model predicts that eastern regions of the Western Palaearctic should contain ancestral populations with range expansions across Europe about 1.6 million years ago and deeper species‐level divergence at both 8–9 and 4–5 million years ago. Sequence data from mitochondrial cytochrome b and multiple nuclear genes showed similar phylogenetic patterns and revealed cryptic genetic species within both morphospecies, indicating greater diversity in these communities than previously thought. Phylogeographic divergence was apparent in most cryptic species between relatively stable, diverse, putatively ancestral populations in Asia Minor and the Middle East, and genetically depauperate, rapidly expanding populations in Europe, paralleling patterns in host gallwasp species. Mitochondrial and nuclear data also suggested that Europe may have been colonized multiple times from eastern source populations since the late Miocene. Temporal patterns of lineage divergence were congruent within and across trophic levels, supporting the Contemporary Host‐tracking Hypothesis for community evolution.