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Integrative approaches have been very useful to identify diagnostic morphological characters in species delimitation and to understand how abiotic factors influence the geographical distribution of taxa and whether these factors may be driving to specific changes in phenotypic variation patterns. Here we use a South American Hypericum species to discuss the importance of such collaborations for taxonomy. The current classification recognizes four sympatric subspecies within Hypericum rigidum; however, due to the presence of intermediary diagnostic characters, a significant number of specimens cannot be assigned to any of these subspecies. Therefore, since the described subspecies are difficult to differentiate, in this study, we applied ecological and morphometric approaches to evaluate whether the infraspecific classification may be sustained in terms of environmental and morphological variation. Applied statistical analyses make evident the high morphological variation within H. rigidum subspecies and the absence of diagnostic characters that sustain the current infraspecific classification. Multivariate analyses also indicate that the morphologic variation of H. rigidum subspecies does not represent adaptive matching of phenotypes to the environment and, therefore, cannot be explained by phenotypic plasticity nor by ecotypic variation. We also discuss the non-standardization of the subspecies concept in plants. In conclusion, H. rigidum subspecies overlap geographically, ecologically and morphologically and, therefore, we recommend that these phenotypes should not be regarded as subspecies, but as part of one single highly variable species.

The combined effects of local adaptation and phenotypic plasticity influencing plant performance are relevant to understand the capacity for genetic responses to climate change. Pinus halepensis is a native species of low- to mid-elevation Mediterranean forests with a high ecological value in drought-prone areas. Thus, it is of utmost importance to determine its adaptive structure for key traits such as growth or survival. Here, we analyse a highly unbalanced dataset collated from different common-garden networks that cover the distribution range of the species. A total of 82 range-wide populations were evaluated in nine Mediterranean trials located in Israel, Italy and Spain. A climate classification of populations allowed for the definition of six different groups, or ecotypes, which showed contrasting performances for tree height and survival at age 15. The effects of ecotypic differentiation and among-ecotypes genetic variation in plasticity were disentangled by fitting stability models accounting for interaction and heteroscedasticity in genotype-by-environment tables. For growth, a Finlay–Wilkinson model suggested high predictability of ecotypic plastic responses in P. halepensis, as described by different linear reaction norms. However, differences in mean height of ca. 15% among ecotypes dominated intra-specific patterns of tree growth across trials, pointing to preponderance of genotypic adaptation over differential ecotypic plasticity in this species. For survival, ecotypic differences were approximately constant across trials, suggesting lack of genotype-by-environment effects. Sub-humid cool climate populations from the eastern Mediterranean (e.g., Greek populations) showed general adaptation and high sensitivity to improved growing conditions, as opposed to populations from the driest ecological extreme of the species (e.g., south Spain and Maghreb populations), which exhibited specific adaptation to harsh environments. Altogether, our results indicate a general adaptive syndrome by which less reactive ecotypes to ameliorated conditions (e.g., non-water-limited) would be associated with high survival rates and low growth. The reported ecotypic differentiation constitutes the basis for tailoring intra-specific responses to climate and disentangling the relationship between adaptive variation and resilience towards climatic warming for this exemplary Mediterranean pine. This study was funded by the Spanish Government (FUTURPIN project, grant number AGL2015-68274-C3-3-R MINECO/FEDER). We acknowledge the collaboration of the Spanish network of forest genetic trials (GENFORED) and especially of Maria Regina Chambel and Eduardo Notivol for data accessing and technical cooperation. GDM wishes to thank Ernesto Fusaro and Francesco Righi (CREA-PLF) for their contribution in gathering data and for establishing the Italian trials. TK wishes to thank the Merle S. Cahn Foundation and the Monroe and Marjorie Burk Fund for Alternative Energy Studies; Mr. and Mrs. Norman Reiser, together with the Weizmann Center for New Scientists; and the Edith & Nathan Goldberg Career Development Chair.

Rocket (Eruca sativa L.) is an old native plant well adapted to diverse climates in Iran. It’s known for the ability to grow and produce seeds rich in protein and oil as well as edible foliage under marginal conditions and has a potential as a promising oil seed. Nonetheless, little is known about its response to salt stress. This study aimed to evaluate possible genetic diversity of local landraces of rocket in terms of salinity tolerance both in germination and whole plant level. In the first experiment, germination characteristics of seven ecotypes of rocket named based on the region of collection as Sirjan, Bardsir, Rigan, Shahdad, Abadeh, Lamerd and Darejove were assayed under increasing salinity from 0 to 18 dS/m. Increasing salinity decreased all germination indices but ecotypes significantly differ in the magnitude of response. Averaged over salinity levels and based on scoring values for final germination percentage, germination rate and seed vigor, one superior (Sirjan), one inferior (Bardsir) and one moderate (Darejove) ecotype were selected for further investigation in the second experiment in which plants were subjected to three salinity levels (1.8, 6 and 12 dS/m) in a hydroculture system and some of their biochemical, physiological and dry matter accumulation attributes were evaluated. Results showed that increasing salinity decreased grain and biological yield, relative water content, leaf chlorophyll content and leaf area but increased leaf carotenoids content, electrolyte leakage, proline and soluble sugars concentrations and shoot and root Na content. Also, in all three ecotypes activities of catalase, superoxide dismutase, guaiacole peroxidase and ascorbate peroxides increased in response to application of 6 or 12 dS/m salinity, but these alterations were not correlated with dry matter or grain production. Na shoot content, however, was closely and negatively associated with grain and biological yield and differ significantly among ecotypes. Interestingly, Bardsir, the least salt tolerant ecotype at germination, was the best in hydroculture experiment and often showed the highest values for the most growth parameters measured. These differential responses suggest a possible change in salt tolerance mechanism along with developmental stages transition.

Under the same environmental conditions, southern and northern populations of temperate and boreal ecosystems exhibit different growth performance. However, which growth trait drives this difference is still unresolved. This study aimed to disentangle the effect of duration and rate of growth on shoot extension of five black spruce [Picea mariana (Mill.)] populations originating from a latitudinal gradient in Quebec, Canada, and growing in a common garden at the southern border of the boreal forest to simulate warming conditions. Bud phenology was monitored weekly during the growing seasons 2017–2019, and shoot length was recorded in autumn, representing annual growth of the primary meristem. Populations originating from the colder sites showed a lower annual shoot increment compared to those originating from the warmer sites. Despite similar durations of bud phenology, the period of shoot extension occurred between the beginning of June and the beginning of July and was longer in the provenances originating from the colder sites. The period of shoot extension, on average, was shortened by 0.9 days for each degree Celsius of increase in annual mean temperature of the site of origin. Moreover, the populations originating from warmer sites showed higher growth rates, which increased by 0.1 cm day−1 for each degree Celsius of increase in the annual mean temperature of the site of origin. Our results confirmed ecotypic variation in growth performance among black spruce populations and demonstrated that differences in shoot length are related to both rate and duration of growth. In the context of a warming climate, northern populations may be unable to reach the current growth performance of southern ones because of their adaptations to harsh local conditions and low intrinsic growth rates.

Colophospermum mopane (J. Kirk ex Benth.) J. Kirk ex J. Leonard occurs over a very large region of southern Africa, occupying varying habitats that could account for ecotypic speciation. This investigation statistical analysed the variations in the architecture of the leaflets of C. mopane from the Limpopo Province of South Africa, with the purpose of ascertaining whether natural variability can act as a source of information for investigating ecotypic variation. Leaf morphometric traits, such as leaflet area, length, width, perimeter, pulvinus angle and the acuteness of the apex, were digitally measured and statistically compared for intra- and inter-population variability. Data indicate that the intra-population variation is 35.33% (statistical similarity: 64.67%), while the inter-population (n = 5) variation is 46.67% (statistical similarity: 53.33%).

Bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey) is an important native bunchgrass for rangeland restoration in western North America. This species is taxonomically complex and has diverged into as many as four subspecies, including subsp. brevifolius, for which four geographically distinct races have been described (A, B, C, and D). Of these four races, only C occurs in the northern Intermountain West. Our objectives were to describe phenotypic and genetic variation within C and to ascertain its taxonomic status. We evaluated 32 populations of C collected across the northern Intermountain West for a battery of biomass, phenological, and functional traits in common-garden settings in the field and greenhouse. Genetic variation was assessed with the use of amplified fragment length polymorphism (AFLP) markers, and correlations were calculated among phenotypic, genetic, environmental, and geographic distance matrices with the use of Mantel tests. Values for these four distance measures were positively correlated, suggesting that environmental heterogeneity and isolation by distance are shaping ecotypic divergence driven by natural selection. We describe three phenotypic zones for C that correspond to previously established ecoregion boundaries. Because genetic data group C apart from subsp. brevifolius races A, B, and D, which originate in the Rocky Mountains and western Great Plains, the so-called race C merits description as a new subspecies apart from subsp. brevifolius.

Origanum vulgare L. subsp. hirtum (Link) Ietsw. is a polymorphic taxon with respect to essential oil production and glandular trichome density. Here it is examined whether the natural populations that are indigenous in continental Greece may be considered as different ecotypes (i.e. populations with different genetic variation) and whether evidence regarding a fitness cost from essential oil production could be obtained. Samples from 30 different natural populations, differing in climatic conditions, were collected across continental Greece in 1998–2000 and were studied for essential oil production and glandular trichome density. Additionally, individual plants, derived from propagated rhizomes, originated from the natural populations, were transplanted in pots in two gardens that varied in terms of mean temperature and aridity. In these experimental populations, the above-ground phytomass and ratio of leaves and inflorescences to above-ground phytomass were additionally measured. The main findings of the study were (a) a strong positive correlation between essential oil concentration and glandular trichome density, (b) a high positive correlation between natural and experimental populations in essential oil concentration (or glandular trichome density), (c) a negative correlation between essential oil concentration and phytomass and (d) a positive relationship between the essential oil concentration and the factors thermal status and summer drought of the location of origin. Results suggest that the examined populations of O. vulgare subsp. hirtum are different ecotypes, the production of essential oils has a cost to plant growth and that the prime target of selection, by producing these oils, is to increase the resistance to drought and heat stresses.

Production of chloroplast-localized small heat-shock proteins (Cp-sHSP) is correlated with increased thermotolerance in plants. Ecotypic variation in function and expression of Cp-sHSPs was analyzed in two Chenopodium album ecotypes from cool vs. warm-temperate USA habitats [New York (NY) and Mississippi (MS) respectively]. Pet was more heat tolerant in the MS than the NY ecotype, and MS ecotype derived proportionally greater protection of Pet by Cp-sHSP during high temperatures. Four genes encoding Cp-sHSPs were isolated and characterized: CaHSP25.99n (NY-1) and CaHSP26.23n (NY-2) from NY ecotype, and CaHSP26.04m (MS-1) and CaHSP26.26m (MS-2) from MS ecotype. The genes were nearly identical in predicted amino-acid sequence and hydrophobicity. Gene expression analysis indicated that MS-1 and MS-2 transcripts were constitutively expressed at low levels at 25 °C, while no NY-1 and NY-2 transcripts were detected at this temperature. Maximum accumulation of NY-1 and NY-2 transcripts occurred at 33 °C and 40 °C for MS-1 and MS-2. Immunoblot analysis revealed that (1) protein expression was highest at 37 °C in both ecotypes, but was greater in MS than NY ecotype at 40 °C; and (2) import of Cp-sHSP into chloroplasts was more heat-labile in NY ecotype. The higher expression of one isoform in MS ecotype may contribute to its enhanced thermotolerance. Absence of correlation between protein and transcript levels, suggests the post-transcriptional regulation is occurring. Promoter analysis of these genes revealed significant variations in heat-shock elements (HSE), core motifs required for heat-shock-factor binding. We propose a correlation between unique promoter architecture, Cp-sHSP expression and thermotolerance in both ecotypes.

Norway spruce ( Picea abies (L.) Karst.) exhibits strong ecotypic variation along altitudinal gradients in morphological traits, e.g. slenderness of crowns or arrangement of second-order branches. We were interested whether montane and lowland morphotypes differ in a key trait for the survival in cold environments, i.e. frost hardiness, and asked: (i) are montane morphotypes more resistant to frost damage and (ii) do they have a lower risk of frost damage by late frosts in spring than lowland morphotypes? We used the electrolyte leakage-method to measure frost hardiness on a monthly basis from October 2006 to May 2007 in stands of the montane and lowland morphotypes at Mt. Brocken in the Harz Mountains, Germany. LT 50 (i.e. the temperature that results in 50% of maximum electrolyte leakage) was assessed by freezing treatments in a frost chamber and was significantly influenced by morphotype, month and minimum ambient temperatures. LT 50 was significantly lower in the montane than in the lowland morphotype, with −107 °C and −49 °C, respectively. However, the interactions between morphotype with minimum ambient temperature or month were not significant. Thus, as frost hardiness of the two morphotypes responded to temperature in the same way, both morphotypes can be supposed to be exposed to the same risk of frost damage during hardening in autumn and dehardening in spring.

Plant populations may adapt to environmental conditions over time by developing genetically based morphological or physiological characteristics. For tidal freshwater forested wetlands, we hypothesized that the conditions under which trees developed led to ecotypic difference in response of progeny to hydroperiod. Specifically, we looked for evidence of ecotypic adaptation for tidal flooding at different salinity regimes using growth and ecophysiological characteristics of two tidal and two non-tidal source collections of baldcypress ( Taxodium distichum (L.) L.C. Rich) from the southeastern United States. Saplings were subjected to treatments of hydrology (permanent versus tidal flooding) and salinity (0 versus ∼2 g l −1 ) for two and a half growing seasons in a greenhouse environment. Saplings from tidal sources maintained 21–41% lower overall growth and biomass accumulation than saplings from non-tidal sources, while saplings from non-tidal sources maintained 14–19% lower overall rates of net photosynthetic assimilation, leaf transpiration, and stomatal conductance than saplings from tidal sources. However, we found no evidence for growth or physiological enhancement of saplings from tidal sources to tide, or of saplings from non-tidal sources to no tide. All saplings growing under permanent flooding exhibited reduced growth and leaf gas exchange regardless of source, with little evidence for consistent salinity effects across hydroperiods. While we reject our original hypothesis, we suggest that adaptations of coastal baldcypress to broad (rather than narrow) environmental conditions may promote ecophysiological and growth enhancements under a range of global-change-induced stressors, perhaps reflecting a natural resilience to environmental change while precluding adaptations for specific flood regimes.

Blackbrush is a dominant shrub species in the transition zone between North American warm and cold deserts. Its seeds are dormant at dispersal and lose dormancy in response to moist chilling. Seeds from warmer low-elevation habitats have shorter chilling requirements and a higher optimum chilling temperature than those from colder habitats where winter snow regularly occurs. This ecotypic variation functions to time germination optimally in habitats with contrasting chilling regimes. Regulation of germination phenology is an important feature of the life history of this ecotonal species, which must be able to migrate elevationally through recruitment from seed in response to long-term climatic shifts in order to survive.

Variation in leaf essential oils and morphometric characters among 38 locations of Chamelaucium uncinatum were used to describe infraspecific diversity and geographic patterns of variation. Four chemical types were designated: citronellal, α -pinene or limonene dominant, or one in which all three monoterpenes were co-dominant. The citronellal and limonene types were geographically restricted but the α -pinene and co-dominant types were widespread. The citronellal type also demonstrated higher diversity (by Shannon–Weiner index) in the oil profile than the other types. Biochemical differentiation was not strongly paralleled by morphological differences between chemotypes; only the citronellal-type differed morphologically from the other three types with respect to floral bud and leaf characters. Based on biochemical and morphological differences, and geographic localization, it was concluded that the citronellal type may represent a recently evolved ecotype of C. uncinatum .

Over the last 15 years New Zealand researchers have been actively involved in the classical biological control of forage weevil pests. In the 1980s, the lucerne pest Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) was successfully suppressed by the parasitoid Microctonus aethiopoides Loan (Hymenoptera: Braconidae). Since 1990, an additional programme has been developed to examine the impact of the recently introduced parasitoid Microctonus hyperodae (Hymenoptera: Braconidae) on New Zealand's worst ryegrass pest, the Argentine stem weevil ( Listronotus bonariensis (Kuschel)). The imported M. hyperodae founder populations were collected from a wide range of ecoclimatic zones. During both of the programmes, the importance of ecotypes has become increasingly apparent. The New Zealand M. aethiopoides population revealed phenological patterns quite different from those observed in Mediterranean Europe, North America and Australia. As a result of these observations, part of the current research into M. hyperodae has been developed specifically to explore ecotypic variation and its implications. This contribution reviews progress to date in researching ecotypic differences and comments on the potential of ecotypes in classical biological control, with particular reference to recently developed DNA-based techniques.

Summary Samples from 42 populations of the annual, hemiparasitic species Euphrasia rostkoviana were collected from nine grassland habitats with different kinds of management. Eleven quantitative characters and the presence or absence of glandular hairs were scored for each plant and six indices were calculated. Populations were mostly polymorphic having plants with or without glandular hairs. The adaptive value of glandular hairs in this situation appeared to be that they protect from water loss. Therefore, the delimitation of E. picta from E. rostkoviana was not possible. Seven ecotypic variants with clear differences in stem length, length and number of cauline internodes, and length and number of branches were delimited. There was evidence of abrupt local differentiation in habit characters between populations of closely adjacent populations from different grassland habitats. A comparison of samples collected over a transect from a mountain pasture and a closely adjacent wet meadow showed intermediate variation of samples from a wet meadow near the ecotone suggesting gene flow might be also important over short distances. There were close relationships between this variation in habit characters and the management regimes of the grasslands. The clinal variation in number of internodes and number of branches appeared to be strongly correlated to a cline in flowering time. An adaptive value of ilie variation in each habit characters was postulated. Grazing and moving as well as competition for light seemed to be ilie major factors for the origin of the close, habitat-correlated variation in the seven ecotypic variants. Therefore, the ecotypic variants of E. rostkoviana confirm the earlier hypothesis of a man-made evolution of parallel ecotypes in many species in different genera of the hemiparasitic Scrophulariaceae. The ecotypic variants were not classified as different infraspecific taxa but were assigned to three earlier delimited subspecies of E. rostkoviana .

Summary Intraspecific differentiation of the worldwide distributed weed Capsella bursa-pastoris has been studied on a local scale. Differentiation patterns are clearly correlated to man made habitats (arable field as opposed to trampling area). a) The seeds of the arable field population seemed to increase germination when covered with soil in contrast to the trampling area population. b) Arable field – early flowering with low variability; greater plant height and more stem branches; larger seed pots; higher seed output. c) Trampling area – late flowering, well developed rosettes; high phenotypic plasticity in begin of flowering, plant height, branching number and fruit dimensions. d) Nutrient supply increased rosette diameter, plant height, number of stem branches, fruit dimensions and seed number within the arable field population, but not the trampling area plants; instead, numbers of rosette leaves and branching number. The reaction norm between the populations was different for some fitness parameters: nutrient supply decreased phenotypic variability in rosette diameter within the arable field population whereas in the trampling area population it decreased phenotypic variability in plant height, branching number and fruit dimensions. Both populations differed significantly in all measured parameters. The relation of characters to habitat is discussed.

Biomass production of different ecotypes within three ecological importantgrass species was determined during cultivation under uniform environmental conditions. Results obtained clearly indicate that ecotypes of these species exhibit a significant degree of variation with regard to biomass production. Furthermore, indications from this investigation are that no correlation exists between production ability of a species and long-term average rainfall, and the effect of both genetic and environmental factors on the production ability of a species determines the eventual biomass production of a species. Biomass production represents one of various ecologically important characteristics to be used in conjunction with other ecological characters to construct a usable, special purpose classification system. This system will assist rangeland ecologists in identifying functional ecotypes within grass species, thus facilitating the understanding and interpretation of vegetation dynamic models and rangeland condition assessments.

Responses of two populations of Melilotus indica (L.) A ll ., one from a non-saline soil and the other from a salt-affected field, to NaCl were assessed in a pot experiment and compared to alfalfa ( Medicago sativa L.) whose salt tolerance had already been determined in a number of previous studies. Both populations of M. indica produced significantly greater shoot fresh and dry biomass than M. sativa after six weeks growth under varying NaCl concentrations. The M. indica population from salt-affected area was slightly superior to that of the normal population. The salt tolerant population of M. indica contained higher amounts of shoot Na + , K + and Ca 2+ contents per plant than M. sativa . Relatively high K/Na and Ca/Na ratios and K versus Na selectivity accounted for its vigorous growth. By contrast, the relatively low biomass producing M. sativa retained large proportions of Na + and Cl − in its roots with little transport of these ions to shoots. Roots also accumulated high amounts of both K + and Ca 2+ which maintained root K/Na and Ca/Na ratios high under saline conditions. The non-saline population of M. indica had similar Na + in the shoots as M. sativa , bud had the highest K/Na ratios. Thus the saline population of M. indica possesses higher salt tolerance than M. sativa . Ecotypic variation in salt tolerance exists in M. indica . In this study salt tolerance of M. indica is associated with ion inclusion and this species maintained shoot K/Na and Ca/Na ratios and K versus Na selectivity high.

Summary Samples from 76 populations of Rhinanthus alectorolophus were collected from localities in the eastern part of Switzerland. A number of morphological characters were measured and an “a priori” classification was tested in a multivariate study. Seven infraspecific groups were delimited and the variation pattern revealed was found to be even more complex than assumed by earlier authors. Floristic composition and the land management of each population was studied; in an analysis with indicator values for eight abiotic factors the habitats of the infraspecific groups were compared. It is demonstrated that there are clear relationships between each of the infraspecific races and their habitats. The differences between infraspecific races have a genotypic basis, and they can be considered to be ecotypes. Land management proves to be the most important factor for habitat delimitation. There are also clear differences in flowering time between the ecotypes with the ecotypes classified into four seasonal groups or as seasonal ecotypes. Some differences between the seasonal ecotypes in individual characters appear to be adaptations to precise habitat conditions. Evidence is presented (for example: clear interrelationships between seasonal ecotypes and their man-made habitats, remarkable recurrent adaptations of ecotypes correlating to the management regime of the habitats in flowering time and some morphological characters) to support the hypothesis of a man-made evolution of parallel seasonal ecotypes in many species of different genera. Morphological and ecological data are used to suggest a hypothesis based upon the effects of man as an influence on the origin of seasonal ecotypes in R. alectorolophus . The evolution of these seasonal ecotypes seems to be due to different kind of selection factors such as cutting, grazing, competition for light or a short vegetation period. Cutting is probably the most important selection factor for the evolution of the ecotypes “alectorolophus” and “mesobromion”. Grazing appears responsible for the evolution of the ecotypes “kemeri” and “patulus” on mountain pastures. Competition for light is likely to be a cause for the evolution of the ecotype “paludosus”. The short vegetation period seems to be important for the evolution of the ecotype “modestus”. “Semleri” is probably the least specialized ecotype because it is found in the least influenced habitats.

Porphyra carolinensis Coll et Cox, an endemic to the southeastern U.S. Atlantic coast, exhibits several attributes which indicate its suitability for mariculture. It tolerates fluctuations of salinity and temperature, persisting in the leafy, blade phase throughout the year in intertidal locations, and it reproduces itself by monospores which develop directly into blades without an intermediate conchocelis phase. Laboratory analysis of isolates from regional populations indicates the presence of genetically based ecotypic variation which can serve as the basis for cultivar selection. Methods are reported for vegetative propagation by spheroplasts under nonaxenic conditions. Isolated cells demonstrated a high degree of survival and totipotency, readily attaching to commercial nylon net where they regenerated the leafy blade phase.