Do plants and animals differ in phenotypic plasticity?

This paper compares the flexibility in the nexus between phenotype and genotype in plants and animals. These taxa although considered to be fundamentally different are found to be surprisingly similar in the mechanisms used to achieve plasticity. Although non-cognitive behaviour occurs in plants, its range is limited, while morphological and developmental plasticity also occur to a considerable extent in animals. Yet both plants and animals are subject to unique constraints and thus need to find unique solutions to functional problems. A true comparison between the plant and animal phenotype would be a comparison between plants and sessile photosynthesizing colonial invertebrates. Such comparisons are lacking. However, they would provide important insights into the adaptive significance of plasticity in these groups. It is also suggested that a comparison of inflexible traits in these groups would provide an understanding of the constraints, as well as the costs and benefits, of a plastic versus non-plastic phenotype in plants and animals.     

Genetic and morphological differentiation in Populus nigra L.: isolation by colonization or isolation by adaptation?

Identifying processes underlying the genetic and morphological differences among populations is a central question of evolutionary biology. Forest trees typically contain high levels of neutral genetic variation, and genetic differences are often correlated with geographic distance between populations [isolation by distance (IBD)] or are due to historic vicariance events [isolation by colonization (IBC)]. In contrast, morphological differences are largely due to local adaptation. Here, we examined genetic (microsatellite) and morphological (from a common garden experiment) variation in Populus nigra L., European black poplar, collected from 13 sites across western Europe and grown in a common garden in Belgium. Significant genetic differentiation was observed, with populations from France displaying greater admixture than the distinct Spanish and central European gene pools, consistent with previously described glacial refugia (IBC). Many quantitative traits displayed a bimodal distribution, approximately corresponding to small‐leaf and large‐leaf ecotypes. Examination of nine climatic variables revealed the sampling locations to have diverse climates, and although the correlation between morphological and climatic differences was significant, the pattern was not consistent with strict local adaptation. Partial Mantel tests based on multivariate summary statistics identified significant residual correlation in comparisons of small‐leaf to large‐leaf ecotypes, and within the small‐leaf samples, but not within large‐leaf ecotypes, indicating that variation within the small‐leaf morphotype in particular may be adaptive. Some small‐leaf populations experience climates very similar to those in large‐leaf sites. We conclude that adaptive differentiation and persistent IBC acted in combination to produce the genetic and morphological patterns observed in P. nigra.     

Genetic Variability of the Grey Wolf Canis lupus in the Caucasus in Comparison with Europe and the Middle East: Distinct or Intermediary Population?

Despite continuous historical distribution of the grey wolf (Canis lupus) throughout Eurasia, the species displays considerable morphological differentiation that resulted in delimitation of a number of subspecies. However, these morphological discontinuities are not always consistent with patterns of genetic differentiation. Here we assess genetic distinctiveness of grey wolves from the Caucasus (a region at the border between Europe and West Asia) that have been classified as a distinct subspecies C. l. cubanensis. We analysed their genetic variability based on mtDNA control region, microsatellite loci and genome-wide SNP genotypes (obtained for a subset of the samples), and found similar or higher levels of genetic diversity at all these types of loci as compared with other Eurasian populations. Although we found no evidence for a recent genetic bottleneck, genome-wide linkage disequilibrium patterns suggest a long-term demographic decline in the Caucasian population – a trend consistent with other Eurasian populations. Caucasian wolves share mtDNA haplotypes with both Eastern European and West Asian wolves, suggesting past or ongoing gene flow. Microsatellite data also suggest gene flow between the Caucasus and Eastern Europe. We found evidence for moderate admixture between the Caucasian wolves and domestic dogs, at a level comparable with other Eurasian populations. Taken together, our results show that Caucasian wolves are not genetically isolated from other Eurasian populations, share with them the same demographic trends, and are affected by similar conservation problems.     

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.     

Urbanization and its effects on personality traits: a result of microevolution or phenotypic plasticity?

Human‐altered environmental conditions affect many species at the global scale. An extreme form of anthropogenic alteration is the existence and rapid increase of urban areas. A key question, then, is how species cope with urbanization. It has been suggested that rural and urban conspecifics show differences in behaviour and personality. However, (i) a generalization of this phenomenon has never been made; and (ii) it is still unclear whether differences in personality traits between rural and urban conspecifics are the result of phenotypic plasticity or of intrinsic differences. In a literature review, we show that behavioural differences between rural and urban conspecifics are common and taxonomically widespread among animals, suggesting a significant ecological impact of urbanization on animal behaviour. In order to gain insight into the mechanisms leading to behavioural differences in urban individuals, we hand‐raised and kept European blackbirds (Turdus merula) from a rural and a nearby urban area under common‐garden conditions. Using these birds, we investigated individual variation in two behavioural responses to the presence of novel objects: approach to an object in a familiar area (here defined as neophilia), and avoidance of an object in a familiar foraging context (defined as neophobia). Neophilic and neophobic behaviours were mildly correlated and repeatable even across a time period of one year, indicating stable individual behavioural strategies. Blackbirds from the urban population were more neophobic and seasonally less neophilic than blackbirds from the nearby rural area. These intrinsic differences in personality traits are likely the result of microevolutionary changes, although we cannot fully exclude early developmental influences.     

Genetic and phenotypic targeting of β-adrenergic signaling in heart failure

Heart failure is a leading cause of hospitalization worldwide. No major significant improvements in prognosis have been achieved for heart failure over the last several decades despite advances in disease management. Heart failure itself represents a final common endpoint for several disease entities, including hypertension and coronary artery disease. On a molecular level, certain biochemical features remain common to failing myocardium. Among these are alterations in the -adrenergic receptor (-AR) signaling cascade. Recent advances in transgenic and gene therapy techniques have presented novel therapeutic strategies for management of heart failure via genetic manipulation of -AR signaling including the targeted inhibition of the -AR kinase (ARK1 or GRK2). In this review, we will discuss the -AR signaling changes that accompany heart failure as well as corresponding therapeutic strategies. We will then review the evidence from transgenic mouse work supporting the use of -AR manipulation in the failing heart and more recent in vivo applications of gene therapy directed at reversing or preventing heart failure. (Mol Cell Biochem 263: 5–9, 2004)     

Invasion strategies in clonal aquatic plants: are phenotypic differences caused by phenotypic plasticity or local adaptation?

Background and Aims

The successful spread of invasive plants in new environments is often linked to multiple introductions and a diverse gene pool that facilitates local adaptation to variable environmental conditions. For clonal plants, however, phenotypic plasticity may be equally important. Here the primary adaptive strategy in three non-native, clonally reproducing macrophytes (Egeria densa, Elodea canadensis and Lagarosiphon major) in New Zealand freshwaters were examined and an attempt was made to link observed differences in plant morphology to local variation in habitat conditions.

Methods

Field populations with a large phenotypic variety were sampled in a range of lakes and streams with different chemical and physical properties. The phenotypic plasticity of the species before and after cultivation was studied in a common garden growth experiment, and the genetic diversity of these same populations was also quantified.

Key Results

For all three species, greater variation in plant characteristics was found before they were grown in standardized conditions. Moreover, field populations displayed remarkably little genetic variation and there was little interaction between habitat conditions and plant morphological characteristics.

Conclusions

The results indicate that at the current stage of spread into New Zealand, the primary adaptive strategy of these three invasive macrophytes is phenotypic plasticity. However, while limited, the possibility that genetic diversity between populations may facilitate ecotypic differentiation in the future cannot be excluded. These results thus indicate that invasive clonal aquatic plants adapt to new introduced areas by phenotypic plasticity. Inorganic carbon, nitrogen and phosphorous were important in controlling plant size of E. canadensis and L. major, but no other relationships between plant characteristics and habitat conditions were apparent. This implies that within-species differences in plant size can be explained by local nutrient conditions. All together this strongly suggests that invasive clonal aquatic plants adapt to a wide range of habitats in introduced areas by phenotypic plasticity rather than local adaptation.     

Multiple unloadings by nectar foragers in honey bees: a matter of information improvement or crop fullness?

Summary When a honey bee forager returns to her hive and unloads nectar, she sometimes transfers her entire load to one bee, but other times she makes a series of unloadings to several bees. One intriguing hypothesis for why foragers make multiple unloadings is the Information Improvement hypothesis: multiple unloadings improve a foragers estimate of the difficulty in finding a receiver bee, and thus of the allocation of labor between nectar collecting and nectar processing. In this paper, we discuss a possible weakness in the empirical evidence in support of the Information Improvement hypothesis. We also present a competing hypothesis, the Crop Fullness hypothesis: multiple unloadings arise from a mismatch between the amount of nectar a forager has to unload and the amount of nectar a receiver can imbibe. Finally, we test the two hypotheses by checking their predictions regarding the conditions under which multiple unloadings occur and which bee (forager or receiver) breaks off the first unloading when a forager makes multiple unloadings. We find that multiple unloadings are common only at times of high nectar influx and that most often it is the receiver, not the forager, who breaks off the first unloading. We argue that both of these findings are contradictory to the Information Improvement hypothesis but are consistent with the Crop Fullness hypothesis. Furthermore, we relate our findings to a recent theoretical study (Gregson et al., 2003) which shows, by means of a simulation model, that the level of multiple unloadings observed can be accounted for by a mismatch between the crop loads of foragers and the crop capacities of receiver bees. We combine our measurements with the Gregson et al. model to identify the rule used by receiver bees in deciding when to stop receiving more nectar. We conclude that receivers make this decision during the course of an unloading, not after completing an unloading. Finally, with this conclusion in hand, we test the Gregson et al. model by comparing predictions and observations on how full receivers are when they decide to break off an unloading. We find a remarkable agreement (prediction: 60%, observation: 52–59%), in strong support of the model.     

Genetic differentiation and connectivity of morphological types of the broadcast‐spawning coral Galaxea fascicularis in the Nansei Islands,Japan

Population connectivity resulting from larval dispersal is essential for the maintenance or recovery of populations in marine ecosystems, including coral reefs. Studies of species diversity and genetic connectivity within species are essential for the conservation of corals and coral reef ecosystems. We analyzed mitochondrial DNA sequence types and microsatellite genotypes of the broadcast‐spawning coral, Galaxea fascicularis, from four regions in the subtropical Nansei Islands in the northwestern Pacific Ocean. Two types (soft and hard types) of nematocyst morphology are known in G. fascicularis and are significantly correlated with the length of a mitochondrial DNA noncoding sequence (soft type: mt‐L; hard type: mt‐S type). Using microsatellites, significant genetic differentiation was detected between the mitochondrial DNA sequence types in all regions. We also found a third genetic cluster (mt‐L+), and this unexpected type may be a cryptic species of Galaxea. High clonal diversity was detected in both mt‐L and mt‐S types. Significant genetic differentiation, which was found among regions within a given type (F_ST = 0.009–0.024, all Ps ≤ 0.005 in mt‐L; 0.009–0.032, all Ps ≤ 0.01 in mt‐S), may result from the shorter larval development than in other broadcast‐spawning corals, such as the genus Acropora. Nevertheless, intraspecific genetic diversity and connectivity have been maintained, and with both sexual and asexual reproduction, this species appears to have a potential for the recovery of populations after disturbance.     

Differences in the onset of laying between island and mainland Mediterranean Blue Tits Parus caeruleus: phenotypic plasticity or genetic differences?

Blue tits Parus caeruleus breeding in deciduous or in evergreen woodlands on the mainland of Europe start to lay 3–4 weeks earlier than Blue Tits on the island of Corsica breeding in evergreen woodlands. A similar difference in average laying date between the two Blue Tit populations has been found in a relatively small sample of captive birds held in outdoor aviaries on the mainland. To provide data on the habitat contrast in Corsica for comparison with that on the mainland, a new study area was started in one of the few deciduous woodlands on Corsica. In addition, new data on laying dates of captive Blue Tits were gathered to increase the sample size of independent pairs in aviaries. This study shows that the habitat effect (deciduous ν evergreen woodland) on the average laying date of Blue Tits is relatively small in comparison with the geography effect (European mainland ν Corsica). The laying date differences between mainland and insular Blue Tits persisted whatever the type of habitat (deciduous, evergreen or outdoor aviaries on the mainland). The data support the hypothesis that the observed differences in the onset of laying between the mainland and insular Blue Tits were mainly influenced by genetic effects and relatively little by non-genetic maternal effects of by genotype—environment interactions.     

Morphotypes,varieties, or subspecies?: genetic diversity and differentiation of four Saintpaulia (Gesneriaceae) morphotypes from the East Usambara Mountains,Tanzania

Saintpaulia (H. Wendl.) is a forest-dependent, endangered plant genus endemic to Tanzania and Kenya. The taxonomy of Saintpaulia from the Usambara Mountains and adjacent lowlands in north-eastern Tanzania is problematic because of the morphological similarity of the species and the presence of considerable intraspecific variation. Conventional molecular phylogenetic methods have failed to reveal the genetic structure of this Saintpaulia complex. In this study, we assessed the genetic composition of 12 Saintpaulia populations, representing four different morphotypes, from the East Usambara Mountains using inter-simple sequence repeat (ISSR) markers. Relatively high genetic diversities were observed within populations (mean h  = 0.320), indicating their adaptive potential. Little genetic differentiation amongst populations (mean F _st  = 0.063) and the genetic divergence of the rosulate and trailing morphotypes support the hypothesis of ongoing divergent evolution within the East Usambara metapopulation(s) of Saintpaulia .  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 347–355.     

Genetic differentiation of island populations: geographical barrier or a host switch?

In the Sonoran desert, there exists a diverse community of cactophilic drosophilids that exploit toxic, rotting cactus tissue as a food resource. The chemistry of the necrotic cactus tissue varies among species, and several drosphilid species have evolved specialized detoxification mechanisms and a preference for certain cactus types. In the present study, we compared the genetic structure of two columnar cactus species, Drosophila mettleri and Drosophila mojavensis, and two prickly pear species, Drosophila mainlandi and Drosophila hamatofila, which have all recently colonized Catalina Island off the coast of southern California. Because there are no columnar cactus species on Catalina Island, the two columnar specialists underwent a host switch to prickly pear cactus, the only cactus present on the island. Previous genetic studies of D. mettleri and D. mojavensis showed significant genetic differentiation between mainland and island populations, which could result from restricted gene flow as a result of the San Pedro Channel, or because of a host switch to prickly pear. To distinguish between these possibilities, we analyzed the genetic structure of the prickly pear species aiming to isolate the effects of geography versus host switching. The results obtained show little to no genetic differentiation for the prickly pear species, supporting the hypothesis that the genetic differentiation of the two columnar species is a result of a host switch from columnar cacti to prickly pear. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Is phenotypic plasticity an explanation for the invasiveness of goldenrods (Solidago and Euthamia) in Europe?

High phenotypic plasticity contributes to invasiveness of alien species. Goldenrods of American origin (Solidago canadensis, S. gigantea and Euthamia graminifolia) have successfully invaded Europe, and this success can be related to their high phenotypic plasticity. The aim of our study was to test the hypothesis of higher phenotypic plasticity of invasive goldenrods by comparing them with native taxa: closely related Solidago virgaurea and similar ecologically, invasive in other regions Tanacetum vulgare. The species studied were grown in a common garden on three different substrates with different fertilizers. After 3 years, the height and number of ramets, biomass production and allocation, phenology and nitrate reductase activity (NRA) were measured. The highest level of phenotypic plasticity was exhibited by the competitively weak native species S. virgaurea. The invasive species produced relatively high biomass and exhibited a moderate level of phenotypic plasticity. Variability in the studied traits did not always correlate with differences in substrates. The invasion success of non-native goldenrods is not caused by their having a higher phenotypic plasticity than native species. Rather, the non-natives should be considered as “Jack of all traits, and master of some”.     

Lack of genetic differentiation among four sympatric southeast African intertidal limpets (Siphonariidae): phenotypic plasticity in a single species?

Specimens of four sympatric intertidal limpet species (Siphonariadayi, S. tenuicostulata, S. anneae and S. nigerrima) were collectedfrom four localities on the east coast of South Africa and southernMozambique. Their phylogenetic relationships were investigatedusing sequences of the mitochondrial COI gene and the intron-containingnuclear ATPSß gene. Two closely related lineages wererecovered, which grouped specimens on the basis of geographyrather than morphology. One lineage was associated with thesubtropical coastline of South Africa's east coast and the otherwith the tropical coastline of northeastern South Africa andsouthern Mozambique. This genetic discontinuity coincides witha biogeographic boundary located in the vicinity of Cape StLucia. Combined genetic diversity of the four species was lowerthan that of three other southern African congeners, and fellwithin the range determined for single southern African marinemollusc species. We suggest that the four limpet species arein fact different morphotypes of a single species. (Received 6 October 2006; accepted 29 March 2007)     

Even more oak species in Mexico? Genetic structure and morphological differentiation support the presence of at least two specific entities within Quercus laeta

Differentiation among populations, sometimes despite ongoing gene exchange, is a key step in speciation. Therefore, comparison of intra- and interspecific differentiation patterns is of great significance to understanding speciation. The genus Quercus is an interesting system to test speciation models in the presence of gene flow, due to its weak interspecific reproductive barriers. The aim of the present study was to characterize the degree and pattern of morphological and genetic differentiation among different morphotypes in the white oak Quercus laeta, some corresponding to the previously described species Quercus centralis, Q. laeta, Quercus prinopsis, and Quercus transmontana, as well as geographically structured variation within Q. transmontana not described previously. Our goal was to evaluate if some of these can be considered distinct specific entities or are rather part of a continuum of variation. Nine microsatellite loci and two intergenic regions of chloroplast DNA were analyzed. Morphological differences were evaluated using geometric morphometrics. Chloroplast DNA showed low differentiation, suggesting introgression or sharing of ancestral haplotypes among the Q. laeta morphotypes. Nuclear microsatellites indicated differentiation into two distinct main genetic groups, which were congruent with morphological differentiation. In conclusion, nuclear markers and morphological variations suggest the existence of at least two different entities within Q. laeta.     

Sympatric morphotypes of the restricted-range Tashan Cave Garra: distinct species or a case of phenotypic plasticity?

Environmental Biology of Fishes - Among Tashan cave barb Garra tashanensis inhabiting a small cave in southwest Iran, two mental disc (sucking mouth disc) forms were observed. To assess their...     

Genetic and phenotypic divergence in an island bird: isolation by distance,by colonization or by adaptation?

Discerning the relative roles of adaptive and nonadaptive processes in generating differences among populations and species, as well as how these processes interact, is a fundamental aim in biology. Both genetic and phenotypic divergence across populations can be the product of limited dispersal and gradual genetic drift across populations (isolation by distance), of colonization history and founder effects (isolation by colonization) or of adaptation to different environments preventing migration between populations (isolation by adaptation). Here, we attempt to differentiate between these processes using island populations of Berthelot's pipit (Anthus berthelotii), a passerine bird endemic to three Atlantic archipelagos. Using microsatellite markers and approximate Bayesian computation, we reveal that the northward colonization of this species ca. 8500 years ago resulted in genetic bottlenecks in the colonized archipelagos. We then show that high levels of genetic structure exist across archipelagos and that these are consistent with a pattern of isolation by colonization, but not with isolation by distance or adaptation. Finally, we show that substantial morphological divergence also exists and that this is strongly concordant with patterns of genetic structure and bottleneck history, but not with environmental differences or geographic distance. Overall, our data suggest that founder effects are responsible for both genetic and phenotypic changes across archipelagos. Our findings provide a rare example of how founder effects can persist over evolutionary timescales and suggest that they may play an important role in the early stages of speciation.     

Jack of all trades,master of some? On the role of phenotypic plasticity in plant invasions

Invasion biologists often suggest that phenotypic plasticity plays an important role in successful plant invasions. Assuming that plasticity enhances ecological niche breadth and therefore confers a fitness advantage, recent studies have posed two main hypotheses: (1) invasive species are more plastic than non-invasive or native ones; (2) populations in the introduced range of an invasive species have evolved greater plasticity than populations in the native range. These two hypotheses largely reflect the disparate interests of ecologists and evolutionary biologists. Because these sciences are typically interested in different temporal and spatial scales, we describe what is required to assess phenotypic plasticity at different levels. We explore the inevitable tradeoffs of experiments conducted at the genotype vs. species level, outline components of experimental design required to identify plasticity at different levels, and review some examples from the recent literature. Moreover, we suggest that a successful invader may benefit from plasticity as either (1) a Jack-of-all-trades, better able to maintain fitness in unfavourable environments; (2) a Master-of-some, better able to increase fitness in favourable environments; or (3) a Jack-and-master that combines some level of both abilities. This new framework can be applied when testing both ecological or evolutionary oriented hypotheses, and therefore promises to bridge the gap between the two perspectives.     

Genetic and phenotypic parameters of body weight in West African Dwarf goat and Djallonké sheep

The International Trypanotolerance Centre's small ruminant breeding programme was initiated in 1995. The aim was to increase the efficiency of meat production and the trypanotolerance of the animals (sheep and goat). To achieve that goal, selection was based on estimated breeding values for daily weight gain from 4 to 12 months of age measured on trypanotolerance challenge. The purpose of this study was to estimate genetic parameters for growth traits and to evaluate genetic trends in West African Dwarf goat and Djallonké sheep resulting from the breeding programme under a low input production environment. Data for West African Dwarf goat and Djallonké sheep included birth weight (BW), weaning weight (W120), yearling weight (W360), pre-weaning (GR0–4) and post-weaning (GR4–12) growth rate. The data were analysed using an animal model that accounted for fixed effects of sex, year of birth, season of birth, parity of the dam, type of birth and the interaction year by season of birth. Estimates of heritability for BW, W120, W360, GR0–4 and GR4–12 were 0.5, 0.43, 0.30, 0.32 and 0.11 for goats and 0.39, 0.54, 0.21, 0.54 and 0.23 for sheep, respectively. The genetic correlation between BW and W120 was high for goats (0.74) and moderate for sheep (0.47). Genetic correlations between W120 and GR4–12 were high (0.92) for goats and moderate (0.49) for sheep. Between GR0–4 and BW the correlation was positive but low for sheep (0.26) and moderate for goats (0.60). Positive trends were found in mean estimated breeding values for animals born in the period 1995–2002 which demonstrated the effectiveness of the implemented breeding programs.