Species Delimitation among Southeastern US Oxyloma (Gastropoda: Succineidae)

The Succineid genus Oxyloma found throughout Canada and United States contains approximately 15 described species whose criterion for differentiation is considered unreliable. As a first step towards understanding the evolutionary history and revising the taxonomy of North American Oxyloma, we have sampled four species found in eastern North America (O. salleana, O. subeffusa, O. effusa, and O. retusa) from their type localities. We used mitochondrial COI, and nuclear LSU sequences with samples found across their range and members of the family to produce a phylogenetic hypothesis of evolutionary relationships and test species boundaries. Molecular phylogeny and species delimitation analyses using mitochondrial and nuclear data finds three monophyletic groups among the four nominal Oxyloma species, confirming doubts concerning the validity of these species

CrossCarry: An R package for the analysis of data from a crossover design with GEE

Experimental crossover designs are widely used in medicine, agriculture, and other areas of the biological sciences. Due to the characteristics of the crossover design, each experimental unit has longitudinal observations and the presence of drag effects on the response variable. There is no package in {R} that clearly models data from crossover designs. The {CrossCarry} package presented in this paper allows testing any crossover design as long as the observed response variable belongs to the exponential family, regardless of whether or not there is a washout period. It also allows modeling repeated measurements within each period and extends the correlation structures used in the generalized estimating equations. The family of correlation structures is built that takes into account the particularities of the design, that is, the correlation between and within the periods. It also includes a parametric component for modeling treatment effects and a non-parametric component for modeling time effects and carry-over effects. The non-parametric component is estimated from splines inserted into the generalized estimation equations

Dairy farmers’ willingness to adopt cleaner production practices for water conservation: A discrete choice experiment in Mejia, Ecuador

Worldwide, farming practices directly impact the quality and quantity of both underground and surface water resources. In Mejia, the leading milk-producing region of Ecuador, the adoption rate of conservation practices among farmers is low despite price incentives established by the Agricultural Ministry. Our discrete choice experiment documents stated preferences for water conservation practices of Mejia’s dairy farmers by facing respondents to alternatives described in terms of water-efficient technologies, management of manure and solid waste, and training to resolve conflicts over water use. Estimates derived from our preferred random parameter logit specification imply that the average willingness to pay (WTP) for a solid rain irrigation system is US$147 ha-1; and US$212 ha-1 for training to resolve conflicts. In addition, we report heterogeneity in WTP estimates. These findings can assist in the resolution of current issues in Mejia, including inefficient water irrigation and weak water governance system. Based on our results and the context of our study area, we suggest, first, the adoption of a cost-sharing scheme (given that the WTP for these practices does not cover their implementation cost), and second, the participation of academic institutions to help these water users resolve conflicts, establish their own rules, and improve water governance