Allometric conservatism in the evolution of bird beaks.

Evolution can involve periods of rapid divergent adaptation and expansion in the range of diversity, but evolution can also be relatively conservative over certain timescales due to functional, genetic-developmental, and ecological constraints. One way in which evolution may be conservative is in terms of allometry, the scaling relationship between the traits of organisms and body size. Here, we investigate patterns of allometric conservatism in the evolution of bird beaks with beak size and body size data for a representative sample of over 5000 extant bird species within a phylogenetic framework. We identify clades in which the allometric relationship between beak size and body size has remained relatively conserved across species over millions to tens of millions of years. We find that allometric conservatism is nonetheless punctuated by occasional shifts in the slopes and intercepts of allometric relationships. A steady accumulation of such shifts through time has given rise to the tremendous diversity of beak size relative to body size across birds today. Our findings are consistent with the Simpsonian vision of macroevolution, with evolutionary conservatism being the rule but with occasional shifts to new adaptive zones.

The evolution of the traplining pollinator role in hummingbirds: specialization is not an evolutionary dead end.

Trapliners are pollinators that visit widely dispersed flowers along circuitous foraging routes. The evolution of traplining in hummingbirds is thought to entail morphological specialization through the reciprocal coevolution of longer bills with the long-tubed flowers of widely dispersed plant species. Specialization, such as that exhibited by traplining hummingbirds, is often viewed as both irreversible and an evolutionary dead end. We tested these predictions in a macroevolutionary framework. Specifically, we assessed the relationship between beak morphology and foraging and tested whether transitions to traplining are irreversible and lead to lower rates of diversification as predicted by the hypothesis that specialization is an evolutionary dead end. We find that there have been multiple independent transitions to traplining across the hummingbird phylogeny, but reversals have been rare or incomplete at best. Multiple independent lineages of trapliners have become morphologically specialized, convergently evolving relatively large bills for their body size. Traplining is not an evolutionary dead end however, since trapliners continue to give rise to new traplining species at a rate comparable to non-trapliners.

Laparoscopic renal surgery.

Renal surgery, radical nephrectomy in particular, was historically the first application of laparoscopic techniques in urology. Since then, laparoscopy has been constantly evolving to claim its position in the surgical armamentarium of the urologist for the treatment of both malignant and benign diseases of the kidney and upper urinary tract. Over the years of increasing surgical experience and exposure, along with the evolution in the techniques and instruments used, laparoscopy has emerged as an equally effective and even more attractive alternative to open surgery for certain indications. The currently available load of literature is able to prove beyond any doubt the oncologic efficacy and minimal morbidity of laparoscopy for the treatment of renal masses in the form of radical or partial laparoscopic nephrectomy and nephroureterectomy. On the other hand, one can claim that laparoscopy is not far from replacing open surgery for the management of benign conditions such as ureteropelvic junction obstruction and donor nephrectomy. This review on laparoscopic renal surgery will discuss the major applications, indications, techniques and outcomes of laparoscopy in the contemporary management of benign and malignant renal diseases while focusing on its benefits and drawbacks compared to open surgery.

Inhibition of arm regeneration by Ophioderma brevispina (Echinodermata, Ophiuroidea) by tributyltin oxide and triphenyltin oxide.

Effects of water-bourne toxicants on regeneration of arms by the brittle star, Ophioderma brevispina, are described. Regeneration was inhibited by 0.1 micrograms liter-1 bis(tri-n-butyltin)oxide and bis(triphenyltin)oxide. Both substances are known to act upon the nervous system, and it is suggested that inhibition was caused by neurotoxicological action of the tin compounds or by their direct effect upon tissue at the breakage point. The former is most likely because regeneration is mediated by the radial nerves of brittle stars.