Experimental tests of bivalve shell shape reveal potential tradeoffs between mechanical and behavioral defenses

Bivalves protect themselves from predators using both mechanical and behavioral defenses. While their shells serve as mechanical armor, bivalve shells also enable evasive behaviors such as swimming and burrowing. Therefore, bivalve shell shape is a critical determinant of how successfully an organism can defend against attack. Shape is believed to be related to shell strength with bivalve shell shapes converging on a select few morphologies that correlate with life mode and motility. In this study, mathematical modeling and 3D printing were used to analyze the protective function of different shell shapes against vertebrate shell-crushing predators. Considering what life modes different shapes permit and analyzing the strength of these shapes in compression provides insight to evolutionary and ecological tradeoffs with respect to mechanical and behavioral defenses. These empirical tests are the first of their kind to isolate the influence of bivalve shell shape on strength and quantitatively demonstrate that shell strength is derived from multiple shape parameters. The findings of this theoretical study are consistent with examples of shell shapes that allow escape behaviors being mechanically weaker than those which do not. Additionally, shell elongation from the umbo, a metric often overlooked, is shown to have significant effects on shell strength.

Ecosystem services and land sparing potential of urban and peri-urban agriculture: A review

Agricultural expansion contributes to the degradation of biodiverse ecosystems and the services these systems provide. Expansion of urban and peri-urban agriculture (UPA), on the other hand, may hold promise to both expand the portfolio of ecosystem services (ES) available in built environments, where ES are typically low and to reduce pressure to convert sensitive non-urban, non-agricultural ecosystems to agriculture. However, few data are available to support these hypotheses. Here we review and summarize the research conducted on UPA from 320 peer-reviewed papers published between 2000 and 2014. Specifically, we explored the availability of data regarding UPA's impact on ES and disservices. We also assessed the literature for evidence that UPA can contribute to land sparing. We find that the growth in UPA research over this time period points to the emerging recognition of the potential role that UPA systems play in food production worldwide. However, few studies (n = 15) place UPA in the context of ES, and no studies in our review explicitly quantify the land sparing potential of UPA. Additionally, while few studies (n = 19) quantify production potential of UPA, data that are necessary to accurately quantify the role these systems can play in land sparing, our rough estimates suggest that agricultural extensification into the world's urban environments via UPA could spare an area approximately twice the size of the US state of Massachusetts. Expanding future UPA research to include quantification of ES and functions would shed light on the ecological tradeoffs associated with agricultural production in the built environment. As food demand increases and urban populations continue to grow, it will be critical to better understand the role urban environments can play in global agricultural production and ecosystem preservation.