DNA markers linked to yield, yield components, and morphological traits in autotetraploid lucerne (Medicago sativa L.)

We have mapped and identifed DNA markers linked to morphology, yield, and yield components of lucerne, using a backcross population derived from winter-active parents. The high-yielding and recurrent parent, D, produced individual markers that accounted for up to 18% of total yield over 6 harvests, at Gatton, south-eastern Queensland. The same marker, AC/TT8, was consistently identified at each individual harvest, and in individual harvests accounted for up to 26% of the phenotypic variation for yield. This marker was located in linkage group 2 of the D map, and several other markers positively associated with yield were consistently identified in this linkage group. Similarly, markers negatively associated with yield were consistently identified in the W116 map, W116 being the low-yielding parent. Highly significant positive correlations were observed between total yield and yield for harvests 1-6, and between total yield and stem length, tiller number, leaf yield/plant, leaf yield/5 stems, stem yield/plant, and stem yield/5 stems. Highly significant QTL were located for all these characters as well as for leaf shape and pubescence.

Minimising cold damage during reproductive development among temperate rice genotypes. II. Genotypic variation and flowering traits related to cold tolerance screening

Low temperature during microspore development increases spikelet sterility and reduces grain yield in rice (Oryza sativa L.). The objectives of this study were to determine genotypic variation in spikelet sterility in the field in response to low-temperature and then to examine the use of physio-morphological traits at flowering to screen for cold tolerance. Multiple-sown field experiments were conducted over 4 consecutive years in the rice-growing region of Australia to increase the likelihood of encountering low-temperature during microspore development. More than 50 cultivars of various origins were evaluated, with 7 cultivars common to all 4 years. The average minimum temperature for 9 days during microspore development was used as a covariate in the analysis to compare cultivars at a similar temperature. The low-temperature conditions in Year 4 identified cold-tolerant cultivars such as Hayayuki and HSC55 and susceptible cultivars such as Sasanishiki and Doongara. After low temperature conditions, spikelet sterility was negatively correlated with the number of engorged pollen grains, anther length, anther area, anther width, and stigma area. The number of engorged pollen grains and anther length were found to be facultative traits as their relationships with spikelet sterility were identified only after cold water exposure and did not exist under non-stressed conditions.

Animal migration: is there a common migratory syndrome?

Ornithologists, and especially northern hemisphere ornithologists, have traditionally thought of migration as an annual return movement of populations between regular breeding and non-breeding grounds. Problems arise because selection does not ordinarily act on populations and because organisms of many taxa (including birds) are clearly migrants, but fail to undertake movements of the kind described. There are also extensive return movements that are not migratory. I propose that it is more useful to think of migration as a syndrome of behavioral and other traits that function together within individuals, and that such a syndrome provides a common ground across taxa from aphids to albatrosses. Large-scale return movements of populations are one outcome of the syndrome. Similar behavioral and physiological traits serve both to define migration and to provide a test for it. I use two insect (Hemipteran) examples to illustrate migratory syndromes and to demonstrate that, in many migrants, behavior and physiology correlate with life history and morphological traits to form syndromes at two levels. I then compare the two Hemipterans with migration in birds, butterflies, and fish to assess the question of whether there are migratory syndromes in common between these diverse migrants. Syndromes are more similar at the level of behavior than when morphology and life history traits are included. Recognizing syndromes leads to important evolutionary questions concerning migration strategies, trade-offs, the maintenance of genetic variance and the responses of migratory syndromes to both similar and different selective regimes.

Phylogeny, evolution and biogeography of the Quadrifoliovariinae Yamaguti, 1965 (Digenea : Lecithasteridae)

The Quadrifoliovariinae is revised and three new species of Quadrifoliovarium Yamaguit, 1965 from acanthurid fishes of the genus Naso from waters of the Indo-Pacific are described: Q, maceria n. sp. from N. tonganus, N. annulatus, N. fageni and N. brevirostris; Q. simplex n. sp. from N. tonganus and N. quannulatus; and Q. quattuordecim n. sp. from N. tonganus. Amendments are made to the characterisation of the Quadrifoliovariinae, Quadrifoliovarium, Bilacinia Manter, 1969 and Unilacinia Manter, 1969 in light of observations on type and new material. A molecular phylogeny based on ITS2 and 28S regions of the ribosomal DNA is proposed. The phylogeny suggests that U. asymmetrica is the most basal taxon and Q. simplex n. sp. and Q. quattuordecim n. sp. the most derived. Evolution of morphological traits within the Quadrifoliovariinae are discussed in light of the molecular phylogeny. Molecular sequences of the ITS2 rDNA were identical between specimens of Q. pritchardae collected off Exmouth (Indian Ocean), Heron Island and Lizard Island (Western Pacific) and Moorea (far Eastern Indo-Pacific), indicating a broad Indo-Pacific distribution. All members of the subfamily are recorded only from the acanthurid genus Naso, with the exception of B. lobatum (Yamaguti, 1970), which has been recorded from a pomacanthid. The restricted host range of the group is discussed in the light of the phylogeny of the host genus Naso.

Predator-induced phenotypic plasticity in tadpoles: extension or innovation?

Phenotypic plasticity, the ability of a trait to change as a function of the environment, is central to many ideas in evolutionary biology. A special case of phenotypic plasticity observed in many organisms is mediated by their natural predators. Here, we used a predator-prey system of dragonfly larvae and tadpoles to determine if predator-mediated phenotypic plasticity provides a novel way of surviving in the presence of predators (an innovation) or if it represents a simple extension of the way noninduced tadpoles survive predation. Tadpoles of Limnodynastes peronii were raised in the presence and absence of predation, which then entered a survival experiment. Induced morphological traits, primarily tail height and tail muscle height, were found to be under selection, indicating that predator-mediated phenotypic plasticity may be adaptive. Although predator-induced animals survived better, the multivariate linear selection gradients were similar between the two tadpole groups, suggesting that predator-mediated phenotypic plasticity is an extension of existing survival strategies. In addition, nonlinear selection gradients indicated a cost of predator-induced plasticity that may limit the ability of phenotypic plasticity to enhance survival in the presence of predators.

Substantial changes in the genetic basis of tadpole morphology of Rana lessonae in the presence of predators

Predator-induced morphological plasticity is a model system for investigating phenotypic plasticity in an ecological context. We investigated the genetic basis of the predator-induced plasticity in Rana lessonae by determining the pattern of genetic covariation of three morphological traits that were found to be induced in a predatory environment. Body size decreased and tail dimensions increased when reared in the presence of preying dragonfly larvae. Genetic variance in body size increased by almost an order of magnitude in the predator environment, and the first genetic principal component was found to be highly significantly different between the two environments. The across environment genetic correlation for body size was significantly below 1 indicating that different genes contributed to this trait in the two environments. Body size may therefore be able to respond to selection independently in the two environments to some extent.