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Common Garden Study (common + garden_study)
Selected AbstractsCOSTS AND LIMITS OF PHENOTYPIC PLASTICITY IN ISLAND POPULATIONS OF THE COMMON FROG RANA TEMPORARIA UNDER DIVERGENT SELECTION PRESSURESEVOLUTION, Issue 6 2009Martin I. Lind Costs and limits are assumed to be the major constraints on the evolution of phenotypic plasticity. However, despite their expected importance, they have been surprisingly hard to find in natural populations. It has therefore been argued that natural selection might have removed high-cost genotypes in all populations. However, if costs of plasticity are linked to the degree of plasticity expressed, then high costs of plasticity would only be present in populations where increased plasticity is under selection. We tested this hypothesis by investigating costs and limits of adaptive phenotypic plasticity in development time in a common garden study of island populations of the common frog Rana temporaria, which have varying levels of development time and phenotypic plasticity. Costs of plasticity were only found in populations with high-plastic genotypes, whereas the populations with the most canalized genotypes instead had a cost of canalization. Moreover, individuals displaying the most extreme phenotypes also were the most plastic ones, which mean we found no limits of plasticity. This suggests that costs of plasticity increase with increased level of plasticity in the populations, and therefore costs of plasticity might be more commonly found in high-plastic populations. [source] Hydraulic differentiation of Ponderosa pine populations along a climate gradient is not associated with ecotypic divergenceFUNCTIONAL ECOLOGY, Issue 4 2002H. Maherali Summary 1.,Pinus ponderosa occurs in a range of contrasting environments in the western USA. Xeric populations typically have lower leaf : sapwood area ratio (AL/AS) and higher whole-tree leaf specific hydraulic conductance (KL) than mesic populations. These climate-driven shifts in hydraulic architecture are considered adaptive because they maintain minimum leaf water potential above levels that cause xylem cavitation. 2.,Using a common garden study, we examined whether differences in biomass allocation and hydraulic architecture between P. ponderosa populations originating from isolated outcrops in the Great Basin desert and Sierran montane environments were caused by ecotypic differentiation or phenotypic plasticity. To determine if populations were genetically differentiated and if phenotypic and genetic differentiation coincided, we also characterized the genetic structure of these populations using DNA microsatellites. 3.,Phenotypic differentiation in growth, biomass allocation and hydraulic architecture was variable among populations in the common garden. There were no systematic differences between desert and montane climate groups that were consistent with adaptive expectations. Drought had no effect on the root : shoot and needle : stem ratio, but reduced seedling biomass accumulation, leaf area ratio, AL/AS and KL. Stem hydraulic conductance (KH) was strongly size-dependent, and was lower in droughted plants, primarily because of lower growth. 4.,Although microsatellites were able to detect significant non-zero (P < 0ˇ001) levels of differentiation between populations, these differences were small and were not correlated with geographic separation or climate group. Estimates of genetic differentiation among populations were low (<5%), and almost all the genetic variation (>95%) resided within populations, suggesting that gene flow was the dominant factor shaping genetic structure. 5.,These results indicate that biomass allocation and hydraulic differences between desert and montane populations are not the result of ecotypic differentiation. Significant drought effects on leaf : sapwood allocation and KL suggest that phenotypic differentiation between desert and montane climates could be the result of phenotypic plasticity. [source] Ecological play in the coevolutionary theatre: genetic and environmental determinants of attack by a specialist weevil on milkweedJOURNAL OF ECOLOGY, Issue 6 2003Anurag A. Agrawal Summary 1We studied the genetic and environmental determinants of attack by the specialist stem-attacking weevil, Rhyssomatus lineaticollis on Asclepias syriaca. 2In natural populations, the extent of stem damage and oviposition were positively correlated with stem width, but not stem height. We hypothesized that both genotypic and environmental factors influencing stem morphology would affect attack by weevils. 3In a common garden study with 21 full-sib families of milkweed, both phenotypic and genetic correlations indicated that weevils impose more damage and lay more eggs on thicker stemmed plants. 4Of three other putative resistance traits, only latex production showed a negative genetic correlation with weevil attack. 5When neighbouring grasses were clipped to reduce light competition, focal milkweed plants received up to 2.6 times the photosynthetically active radiation and 1.6 times the red to far red ratio of light compared with plants with intact grass neighbours. Focal milkweed plants were therefore released from the classic neighbour avoidance response and had 20% shorter internode lengths, were 30% shorter, and had 90% thicker stems compared with controls. 6Clipping of grass neighbours resulted in nearly 2.7 times the damage and oviposition by stem weevils, thus supporting the hypothesis of an environmental or trait-mediated indirect influence on resistance. 7Although attack of plants by weevils strongly increases the probability of stem mortality, thicker stems experience lower mortality, thus counteracting the selective impact of weevil-induced plant mortality. 8The determinants of attack on milkweeds include both genetic variation for stem thickness and an indirect environmental influence of plant neighbours. If milkweeds and weevils are coevolving, the interaction is diffuse because the ecological neighbourhood is likely to modify the patterns of reciprocal natural selection. [source] The invasive alien leaf miner Cameraria ohridella and the native tree Acer pseudoplatanus: a fatal attraction?AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2010Christelle Péré 1The horse-chestnut leaf miner Cameraria ohridella is an invasive moth in Europe and a serious pest of horse-chestnut Aesculus hippocastanum. The moth also occasionally attacks sycamore maple Acer pseudoplatanus, when situated beside infested horse-chestnuts. 2The main objective of the present study was to provide an overview of the relationship between C. ohridella and A. pseudoplatanus and to determine whether C. ohridella has the potential to shift to this native tree. 3In the field, females oviposit on different deciduous tree species. Although less frequently attacked than A. hippocastanum, A. pseudoplatanus was clearly preferred for oviposition over 12 other woody species investigated. 4Surveys in Europe demonstrated that the majority of A. pseudoplatanus trees found beside infested A. hippocastanum had mines of C. ohridella, even though more than 70% of the larvae died within the first two instars. Attack rates and development success greatly varied from site to site. Attack levels on A. pseudoplatanus were not always correlated with those on A. hippocastanum, and mines on A. pseudoplatanus were sometimes observed beside weakly-infested A. hippocastanum. 5Field observations, experimental exposure of A. pseudoplatanus saplings and rearing trials in a common garden study showed that individual trees may vary in their susceptibility to C. ohridella, whereas there was no evidence that C. ohridella populations vary in their performance on A. pseudoplatanus. 6To date, there is little evidence that C. ohridella represents a major risk for A. pseudoplatanus. [source] | ||||||||||