Size,structure and nitrogen content of seeds of Fabaceae in relation to nodulation

Looking for clues to explain the low rate and unpredictability of the pollination of allogamous, epiphytic orchids in the context of the success of the orchid family in general, we compared the pollination of two miniature twig epiphytes in Mexico: Notylia barkeri, a ‘weedy’, rewarding species, and Erycina crista‐galli, a rare, deceptive species. We measured the effects of the spatial organization of the flowers and various parameters of visibility and height above the ground in relation to the spatial organization of the seed capsules (which retrospectively measures the activity of the pollinators). The spatial presentation of the flowers of E. crista‐galli explained only 5% of the distribution of the seed capsules. For N. barkeri, with compound flowers, the spatial presentation, considering individual flowers or inflorescences, explained 12% and 45% of the distribution of the seed capsules, respectively, and all other interactions between the variables were insignificant. Both the deceptive and reward strategies resulted in the production of large numbers of seeds despite a low pollination percentage (1–5%). Notylia barkeri produced 11.8 (2005–6) and 53.7 (2007–8) times more seeds in total than E. crista‐galli. Furthermore, unlike E. crista‐galli, N. barkeri responded to loss of individuals after high winds with an increased production of flowers per plant. We suggest that orchids have evolved to specialize in chance, and instead of maximizing pollinator attraction, they maximize the seed production resulting from every casual encounter. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 165 , 251–266.     

Vicariance and convergence in Magellanic and New Zealand long‐looped brachiopod clades (Pan‐Brachiopoda: Terebratelloidea)

Phylogenetic reconstructions using parsimony, maximum likelihood (ML), and Bayesian relaxed molecular clock analyses of ～2850 nucleotides of nuclear‐encoded small and large subunit ribosomal DNAs (SSU and LSU rDNAs) from 14 long‐looped (terebratelloid) ingroup and four short‐looped (terebratulidine) outgroup brachiopod taxa, together with ML analyses of ～663 nucleotides of mitochondrial cytochrome oxidase subunit 1 (cox1) from 12 terebratelloid taxa, show that deep divergence separates taxa endemic to waters in the vicinity of New Zealand from those with a Magellanic distribution around South America and Antarctica. This deep divergence also separates Magellanic Terebratella dorsata from New Zealand Terebratella sanguinea, showing that they are not congeneric. Instead, they belong to separate ‘Magellanic’ (MAG) and ‘New Zealand’ (NZ) clades that first diverged about 82 Mya (95% highest posterior density, 48–120 Mya), correlating with separation between the NZ and Antarctic tectonic plates. Sequence analyses also reveal (1) that the Antarctic endemic taxa Magellania fragilis and Magellania joubini are not congeneric with Magellania venosa, suggesting that their previous placement in Aerothyris should be restored, and (2) that divergence between Antarctic and NZ species of the terebratulide Liothyrella occurred much later than plate separation, perhaps because of continuing gene flow caused by long‐lived larvae. The topology of the rDNA and cox1 gene trees implies that radial ornament of the shell (‘ribbing’) has been gained (and/or lost) independently within the MAG and NZ clades. Radial ribs are widespread in articulate brachiopods throughout the Phanerozoic, but no comparisons of brachiopod rib morphology and morphogenesis have been published. Our comparisons of transverse shell mid‐sections in the scanning electron microscope reveal no obvious evidence of differences in morphology between independently gained ribs. We also consider several ways in which ribs may affect fitness, including effects on hydrodynamics. Only scanty and inconclusive evidence is available, but we suggest that effects (if any) are likely to be of small magnitude; adaptive value of brachiopod shell ribs remains to be demonstrated. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162 , 631–645.     

Seed ecology of a Mediterranean perennial herb with an exceptionally extended flowering and fruiting season

Lobularia maritima is a Mediterranean short-lived herb with a flowering and fruiting season that lasts for ten months. Previous studies have shown that recruitment in periods other than autumn of the flowering season has few demographic implications; that is contributes little to the population growth rate. Since environmental conditions in periods other than autumn would allow recruitment, we examined to what extent the seed ecology of L. maritima accounts for recruitment shortage for the greater part of the year. To this end, we studied the effects of selfing and outcrossing on seed production and germination, within- and between-year variation in seed mass and germination, seed characteristics in the soil seed bank throughout the year, and the effect of temperature as a factor controlling seed germination. Results indicate that selfing does not decrease recruitment, and thus the observed changes in visitation rate and pollinator composition throughout the year cannot account for differences in recruitment. Germinability decreases throughout the year, suggesting a possible cost in reproduction associated with extended flowering. L. maritima has a transient seed bank whose seeds also experience a decrease in their germination throughout the year. Finally, temperature affects seed germination patterns, indicating the existence of quiescence mechanisms that prevent germination in the months prior to the summer drought. Overall, the results obtained support and, at least partly, explain the recruitment patterns of L. maritima observed in the field.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 273–280.     

Plasticity to simulated shade is associated with altitude in structured populations of Arabidopsis thaliana

Plants compete for photosynthesis light and induce a shade avoidance syndrome (SAS) that confers an important advantage in asymmetric competition for light at high canopy densities. Shade plasticity was studied in a greenhouse experiment cultivating Arabidopsis thaliana plants from 15 populations spread across an altitudinal gradient in the northeast area of Spain that contain a high genetic variation into a reduced geographical range. Plants were exposed to sunlight or simulated shade to identify the range of shade plasticity. Fourteen vegetative, flowering and reproductive traits were measured throughout the life cycle. Shade plasticity in flowering time and dry mass was significantly associated with the altitude of population origin. Plants from coastal populations showed higher shade plasticity indexes than those from mountains. The altitudinal variation in flowering leaf plasticity adjusted negatively with average and minimum temperatures, whereas dry mass plasticity was better explained by negative regressions with the average, maximum and minimum temperatures, and by a positive regression with average precipitation of the population origin. The lack of an altitudinal gradient for the widest number of traits suggests that shade light could be a driver explaining the distribution pattern of individuals in smaller geographical scales than those explored here.     

Primary growth and morphological markers of interannual growth limits in Cupressaceae from Patagonia

The present study shows experimentally that primary growth of the native Patagonian Cupressaceae Austrocedrus chilensis (D. Don) Pic.-Serm et Bizz., Fitzroya cupressoides (Molina) I. M. Johnst. and Pilgerodendron uviferum (D. Don) Florin is potentially continuous. External morphological markers of interannual growth limits have been identified for the main axes of these species after several years of observation. Such limits correspond with axis portions in which internodes are relatively short and leaves have a small distal free end forming an acute angle with the axis. The causality of these results and their utility for studying the productivity, adaptation to different environments, population management and conservation of these threatened species are discussed.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 146 , 285–293.     

A new aglaspidid arthropod from the Upper Cambrian of Tasmania

Abstract: The aglaspidid arthropod, Australaglaspis stonyensis gen. et sp. nov., is described from the Idamean (Upper Cambrian) of Stony Point, Montagu, north‐western Tasmania. The dorsal exoskeleton comprises a semicircular cephalon with a well‐defined marginal rim, acute genal angles, oval eyes, subtriangular glabella area and a subtrapezoidal hypostome. The trunk bears eleven somites with well‐developed pleural spines that progressively curve backwards. Paired postventral plates cover the last trunk tergites and the base of the tailspine, which is long and characterized by a medial cleft. Bilobed ventral impressions indicate the presence of homopodous appendages, forming a food groove along the trunk. The fossil assemblage and its mode of preservation suggest that Australaglaspis originally possessed a phosphatic cuticle, but chemical traces of it have been lost because of regional metamorphism and weathering. Australaglaspis appears to be closely related to the North American aglaspidid Chraspedops modesta Raasch, 1939, based on its medially cleft tailspine.