Putting plant resistance traits on the map: a test of the idea that plants are better defended at lower latitudes.

• It has long been believed that plant species from the tropics have higher levels of traits associated with resistance to herbivores than do species from higher latitudes. A meta-analysis recently showed that the published literature does not support this theory. However, the idea has never been tested using data gathered with consistent methods from a wide range of latitudes. • We quantified the relationship between latitude and a broad range of chemical and physical traits across 301 species from 75 sites world-wide. • Six putative resistance traits, including tannins, the concentration of lipids (an indicator of oils, waxes and resins), and leaf toughness were greater in high-latitude species. Six traits, including cyanide production and the presence of spines, were unrelated to latitude. Only ash content (an indicator of inorganic substances such as calcium oxalates and phytoliths) and the properties of species with delayed greening were higher in the tropics. • Our results do not support the hypothesis that tropical plants have higher levels of resistance traits than do plants from higher latitudes. If anything, plants have higher resistance toward the poles. The greater resistance traits of high-latitude species might be explained by the greater cost of losing a given amount of leaf tissue in low-productivity environments.

Cross-habitat variation in the phenology of a colonial spider: insights from a reciprocal transplant study.

In species with widespread distribution, populations found in markedly different environments can show differences in developmental traits. This, in time, can have an effect on reproductive success. Sources of variation in developmental traits can be genetic or environmentally induced. I examined the relationship between environmental and genetic influences on juvenile development in populations of the colonial spider, Parawixia bistriata, located at sites with different moisture regimes and associated environmental variables (e.g., prey availability). It was expected that individuals from different populations would show differences in developmental traits and that those differences will be associated with lower reproductive success at dry sites. I recorded the phenology and developmental traits of native and transplanted individuals in the field and estimated reproductive success based on clutch size. Colonies from wet versus dry sites showed different phenologies, with individuals at dry sites maturing later. Transplant results suggest plasticity in instar duration caused by environmental effects. Despite differences in resources and spider phenology, clutch sizes of native dry and wet populations were similar. Transplanted individuals, however, were differentially affected. Transplants from wet to dry sites (WD) showed lower growth rates and smaller clutches, whereas transplants from dry to wet sites had larger clutch sizes than in native habitat. Delayed maturation and failure to reproduce in WD individuals is associated with a lower tendency to capture prey in groups and less aggressive interactions during prey capture. Thus, despite negative environmental effects on development, dry native individuals have evolved non-developmental traits that allow successful reproduction.