Summary• 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 highlatitude 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.

SummaryMost plant species have a range of traits that deter herbivores. However, understanding of how different defences are related to one another is surprisingly weak. Many authors argue that defence traits trade off against one another, while others argue that they form coordinated defence syndromes.We collected a dataset of unprecedented taxonomic and geographic scope (261 species spanning 80 families, from 75 sites across the globe) to investigate relationships among four chemical and six physical defences.Five of the 45 pairwise correlations between defence traits were significant and three of these were tradeoffs. The relationship between species' overall chemical and physical defence levels was marginally nonsignificant (P = 0.08), and remained nonsignificant after accounting for phylogeny, growth form and abundance. Neither categorical principal component analysis (PCA) nor hierarchical cluster analysis supported the idea that species displayed defence syndromes.Our results do not support arguments for tradeoffs or for coordinated defence syndromes. Rather, plants display a range of combinations of defence traits. We suggest this lack of consistent defence syndromes may be adaptive, resulting from selective pressure to deploy a different combination of defences to coexisting species.

The augochlorine (Halictidae) bee genus Xenochlora is the diurnal sister group to the nocturnal Megalopta, both of which are stem-nesting halictid bees. Here we present notes on the nesting biology and social behavior in four nests of Xenochlora nigrofemorata and one nest of X. ianthina from Madre de Dios, Peru. All nests contained multiple females and dissections of X. nigrofemorata indicated within nest reproductive differentiation among females that is associated with body size. Size variation among females is conspicuous and a variety of morphometrics are examined to document it. A genal index is used to describe cephalic variation, and results are compared with seven other halictine bees. All morphometrics were investigated for measurement error. Nests of Xenochlora appear to be founded by single females and multifemale nests clearly exhibit parasocial behavior and we hypothesize that they temporally switch between semisocial, eusocial and possibly communal phases.KEYWORDS: Halictidae, Augochlorini, Xenochlora, social evolution, size variation, stem nest RESUMEN: El genero de abejas Xenochlora (Augochlorini, Halictidae) es el grupo hermano diurno del genero nocturno Megalopta. Ambos grupos son abejas que construyen sus nidos en madera en descomposicion. Aqui presentamos anotaciones sobre la biologia de anidacion y comportamiento social en cuatro nidos de Xenochlora nigrofemorata y un nido de X. ianthina en Madre de Dios, Peru. Todos los nidos contenian multiples hembras y las disecciones de X. nigrofemorata indican que hay diferenciacion reproductiva entre las hembras de un nido, asociada con el tamaho del cuerpo. El polimorfismo entre las hembras es evidente y una serie de mediciones morfometricas son examinadas para documentar la variation en tamaho. Un indice genal es utilizado para describir el polimorfismo cefalico y los resultados son comparados con otras especies de abejas halictidas. Todas las mediciones morfometricas fueron analizadas para determinar el error de medicion. Los nidos de Xenochlora parecen ser fundados por hembras solitarias y los nidos con hembras multiples exhiben claramente un comportamiento parasocial y es posible que temporalmente intercambien entre fases semisocial, eusocial y posiblemente comunal.

Bees of the genus Megalopta have gained attention as a result of their social nesting and nocturnal foraging. Seventeen nests of Meglaopta atra from the highlands of Chiriqui Province, Panama, were collected at the end of the dry season when brood rearing is expected to be at its peak. Most nests contained single females; within multifemale nests only one female possessed enlarged ovarioles, although some non-reproductive individuals were inseminated. In two of these nests reproductive individuals were clearly larger in body size than nestmates, but body size variation and macrocephaly were equivalent to those found in other Neotropical augochlorines. There was no evidence of a nonreproductive worker-like caste and multifemale nests did not appear to be more productive than solitary nests, which may represent pre-reproductive assemblages. Megalopta atra appears to be isolated by altitude from co-geners common in Panama, this is discussed in comparison with temperate halictine bees, in which environmental dines separate solitary from social populations.