Vocal repertoire of cooperatively breeding Smooth‐billed Anis

Calls are functionally diverse signals that mediate behavior in a wide variety of contexts in both passerines and non‐passerines. However, the call‐based acoustic communication systems of non‐passerines have received less attention from investigators than those of passerines. We examined the vocal repertoire of Smooth‐billed Anis (Crotophaga ani), cooperatively breeding cuckoos that live in groups with multiple breeding pairs. We recorded calls from 22 groups over two breeding seasons at the Cabo Rojo National Wildlife Refuge in Puerto Rico. We identified 11 call types and one group vocalization, and used an automated sound measurement program to quantify their acoustic features. Discriminant function analysis (DFA) correctly classified 74.2% of calls based on these features. The vocal repertoire of Smooth‐billed Anis is larger than that reported for the three other species in the subfamily Crotophaginae. Smooth‐billed Anis have at least two alarm calls, two nest‐specific calls, and one nest defense call. We also identified one possible signal of aggressive intent, one possible appeasement signal, and two calls that may communicate identity. The relatively large vocal repertoire of Smooth‐billed Anis and association of distinct call types with different functions and contexts supports the main prediction of the social complexity hypothesis, i.e., species with more complex social systems will have more complex communication systems.     

Different functional roles of RTR complex factors in DNA repair and meiosis in Arabidopsis and tomato

The RTR (R ecQ/Top 3/Rmi 1) complex has been elucidated as essential for ensuring genome stability in eukaryotes. Fundamental for the dissolution of Holliday junction (HJ)-like recombination intermediates, the factors have been shown to play further, partly distinct roles in DNA repair and homologous recombination. Across all kingdoms, disruption of this complex results in characteristic phenotypes including hyper-recombination and sensitivity to genotoxins. The type IA topoisomerase TOP3α has been shown as essential for viability in various animals. In contrast, in the model plant species Arabidopsis, the top3α mutant is viable. rmi1 mutants are deficient in the repair of DNA damage. Moreover, as opposed to other eukaryotes, TOP3α and RMI1 were found to be indispensable for proper meiotic progression, with mutants showing severe meiotic defects and sterility. We now established mutants of both TOP3α and RMI1 in tomato using CRISPR/Cas technology. Surprisingly, we found phenotypes that differed dramatically from those of Arabidopsis: the top3α mutants proved to be embryo-lethal, implying an essential role of the topoisomerase in tomato. In contrast, no defect in somatic DNA repair or meiosis was detectable for rmi1 mutants in tomato. This points to a differentiation of function of RTR complex partners between plant species. Our results indicate that there are relevant differences in the roles of basic factors involved in DNA repair and meiosis within dicotyledons, and thus should be taken as a note of caution when generalizing knowledge regarding basic biological processes obtained in the model plant Arabidopsis for the entire plant kingdom.     

Inferring causal factors for a declining population of bottlenose dolphins via temporal symmetry capture–recapture modeling

We applied temporal symmetry capture–recapture (TSCR) models to assess the strength of evidence for factors potentially responsible for population decline in bottlenose dolphins (Tursiops truncatus) in Doubtful Sound, New Zealand from 1995 to 2008. Model selection was conducted to estimate recruitment and population growth rates. There were similar levels of support for three different models, each reflecting distinct trends in recruitment. Modeling yielded low overall estimates of recruitment (0.0249, 95% CI: 0.0174–0.0324) and population growth rate (0.9642, 95% CI: 0.9546–0.9737). The TSCR rate of population decline was consistent with an estimate derived from trends in abundance (lambda = 0.9632, 95% CI: 0.9599–0.9665). The TSCR model selection confirmed the influence of a decline in the survival of calves (<1 yr old) since 2002 for population trends. However, TSCR population growth rates did not exceed 1 in any year between 1995 and 2008, indicating the population was declining prior to 2002. A separate reduction in juvenile survival (1–3 yr old) prior to 2002 was identified as a likely contributing factor in the population decline. Thus, TSCR modeling indicated the potential cause of the population decline in Doubtful Sound: cumulative impacts on individuals <3 yr old resulting in a reduced recruitment.     

Genomics outperforms genetics to manage mistakes in fisheries stocking of threatened species

Biodiversity and Conservation - Hatchery production and fisheries stocking is a widespread and high profile management practice because it allows recreational fisheries to continue in threatened...     

A mathematical model for the mechanical properties of scallop shells

The mechanical behaviour of one or both shell valves of five species of pectinacean and one anomiacean was determined using strain gauge rosettes attached to the inner surfaces of the valves. A multiple linear regression analysis accounted for over 64% of the total vanance in tensile shell compliance. The important shell architectural variables were thickness, corrugation and, much less important, convexity and shell length. Calculation showed that in general corrugation of the shell was easily the cheapest way of producing stiffness, in terms of the amount of shell material required. Suggestions are offered as to why not all scallops are scalloped.     

The mechanical design of the tusk of the narwhal (Monodon nonoceros: Cetacea)

The mechanical properties of the tissues of the tusk of a narwhal Monodon monoceros , their histological arrangement, and the gross anatomy of the tusk were examined. The histology of the tusk shows various toughening mechanisms. The tusk tissues are of low stiffness, but are very tough, suiting the tusks for loading on impact, but not for longitudinal loading. These mechanical properties suggest the possible functions of the tusk, namely to be long in order to be sexually attractive, while being tough in order to withstand 'testing' blows from other males.     

A computational procedure for assessing the significance of RNA secondary structure

In our recent series of papers, we have used the structuresof statistical significance from Monte Carlo simulations toimprove the predictions of secondary structure of RNA and toanalyze the possible role of locally significant structuresin the ljfe cycle of human immunodeficiency virus. Because ofintensive computational requirements for Monte Carlo simulation,it becomes impractical even using a supercomputer to assessthe significance of a structure with a window size > 200along an RNA sequence of 1000 bases or more. In this paper,we have developed a new procedure that drastically reduces thetime needed to assess the significance of structures. In fact,the efficiency of this new method allows us to assess structureson the VAX as well as the CRAY Received on May 11, 1989; accepted on August 22, 1989