Maize dependence or market integration? Caries prevalence among indigenous maya communities with maize‐based versus globalized economies

The relationship between diet and oral health is widely known, yet data on dental caries prevalence is lacking for many indigenous groups with traditional or rapidly modernizing diets. This research documents caries prevalence in two Maya communities from northern Yucatán (Mexico) with significantly different levels of market integration, subsistence, and diet: Yalsihón, with a traditional, maize‐based subsistence economy, and Dzilam, with access to globalized food markets. Each sample was subdivided by sex into 15–19, 20–24, and 25–30 years‐of‐age classes. Caries prevalence was considered separately both when the lesion affected the enamel superficially (grade 1+) and when it reached the dentin (grade 2+). In both villages, females of all age classes manifest more caries than males. Results show higher prevalence of caries at Dzilam than at Yalsihón, except for grade 1+ caries among 15–19‐year‐old males and grade 2+ caries among 15–19‐year‐old females. Though differences are not significant, earlier pregnancies among 15–19‐year‐old females at Yalsihón could be a causative factor. A survey indicated a more balanced diet at Yalsihón despite a heavier intake of maize than at Dzilam. Striking differences were documented in the ingestion of soda and globalized foods; sodas were virtually absent at Yalsihón, while at Dzilam they were ingested daily in great quantities. The decline in oral health at Dzilam is inferred to result from consumption of industrially processed foods and drinks, while a traditional diet leads to less caries despite daily heavy consumption of maize, which must be considered when interpreting caries rates in archaeological samples. Am J Phys Anthropol 153:190–202, 2014. © 2013 Wiley Periodicals, Inc.     

Changes in Elephant Abundance Affect Forest Composition or Regeneration?

While overall numbers of African elephant have declined dramatically in recent times, some populations are now confined to protected areas and are locally overabundant—an undesirable situation for both biodiversity conservation and elephants. In forested protected areas, options to manage elephants are limited because it is difficult to safely approach animals, yet it is vital that these populations are managed because browsing by elephants can dramatically alter forest ecosystems. Using data collected over 50 yr in Kibale National Park, Uganda, we examine the prediction that increasing elephant numbers and associated changes in their foraging behavior have caused a shift in tree community composition. Although the relative abundance of elephants increased significantly between 1996 and 2010, the population structure of their preferred tree food species did not change, nor did tree community composition change in favor of species able to re‐sprout after elephant damage. Furthermore, over the last 50 yr Kibale elephants have not become more selective foragers, as would be expected if more nutritious tree species were declining. However, elephants are more abundant in disturbed areas dominated by shrubs and grasses and appear to have arrested forest succession in these areas. At their current abundance, elephants have not selectively altered the composition of intact old growth forest, but they do inhibit the regeneration of disturbed areas.     

Horn growth rate and longevity: implications for natural and artificial selection in thinhorn sheep (Ovis dalli)

We used horn measurements from natural and hunted mortalities of male thinhorn sheep Ovis dalli from Yukon Territory, Canada, to examine the relationship between rapid growth early in life and longevity. We found that rapid growth was associated with reduced longevity for sheep aged 5 years and older for both the hunted and natural mortality data sets. The negative relationship between growth rate and longevity in hunted sheep can at least partially be explained by morphologically biased hunting regulations. The same trend was evident from natural mortalities from populations that were not hunted or underwent very limited hunting, suggesting a naturally imposed mortality cost directly or indirectly associated with rapid growth. Age and growth rate were both positively associated with horn size at death for both data sets, however of the two growth rate appeared to be a better predictor. Large horn size can be achieved both by individuals that grow horns rapidly and by those that have greater longevity, and the trade-off between growth rate and longevity could limit horn size evolution in this species. The similarity in the relationship between growth rate and longevity for hunted and natural mortalities suggests that horn growth rate should not respond to artificial selection. Our study highlights the need for the existence and study of protected populations to properly assess the impacts of selective harvesting.     

The effect of seasonal variation in abiotic factors on fish community structure in temporary and permanent pools in a tropical wetland

1. Fish community structure depends on biotic interactions and abiotic variables. Abiotic variables appear to gain importance in highly variable freshwater systems, such as tropical wetlands where a marked seasonal hydroperiod (dry and wet seasons) modifies water quality and quantity, differentially affecting fish survival and, consequently, modifying species richness and abundance. 2. We evaluated the relationship between abiotic variables and fish community structure in variable (temporary) and stable (permanent) pools that were interconnected in a tropical wetland with marked annual dry and wet seasons. 3. All fish species were able to occupy any of the studied pools, but our results showed distinctive fish community structures in permanent and temporary pools. Community structure was related to temperature, depth, pH and macrophyte coverage. Total fish abundance in the wetland was negatively related to water depth and positively related to macrophyte coverage. 4. Null models of co‐occurrence indicated a non‐random pattern at the wetland scale and a random pattern within groups of pools with similar characteristics, suggesting that fish communities are structured according to habitat features. We conclude that seasonal abiotic variation and habitat characteristics in this highly variable pristine wetland play major roles in structuring fish communities.