Evolution of Autonomous Selfing in Marginal Habitats: Spatiotemporal Variation in the Floral Traits of the Distylous Primula wannanensis

Outcrossing plant species are more likely to exhibit autonomous selfing in marginal habitats to ensure reproduction under conditions of limited pollinator and/or mate availability. Distyly is a classical paradigm that promotes outcrossing; however, little is known about the variation in floral traits associated with distylous syndrome in marginal populations. In this study, we compared the variation in floral traits including stigma and anther height, corolla tube length, herkogamy, and corolla diameter between the central and peripheral populations of the distylous Primula wannanensis, and assessed the variation of floral traits at early and late florescence stages for each population. To evaluate the potential consequences of the variation in floral traits on the mating system, we investigated seed set in each population under both open-pollinated and pollinator-excluded conditions. The flower size of both short- and long-styled morphs was significantly reduced in late-opening flowers compared with early opening flowers in both central and peripheral populations. Sex-organ reciprocity was perfect in early opening flowers; however, it was largely weakened in the late-opening flowers of peripheral populations compared with central populations. Of these flowers, disproportionate change in stigma height (elongated in S-morph and shortened in L-morph) was the main cause of reduced herkogamy, and seed set was fairly high under pollinator-excluded condition. Our results provide empirical support for the hypothesis on the evolution of delayed autonomous selfing in marginal populations of distylous species. Unsatisfactory pollinator service is likely to have promoted reproductive assurance of distylous plants with largely reduced herkogamy mimicking “homostyles.”

Persistence of Corals in Marginal Habitats: the Role of the Environment, and Symbiont Diversity and Ecophysiology

<p>Many corals live in marginal habitats, close to their survival thresholds of water temperature, light penetration and aragonite saturation. Living under these highly variable and extreme conditions is likely facilitated by specific physiological adaptations and/or the presence of unique species of coral and their symbionts but data on these factors are limited. The specific objectives of the study were to: (1) examine the diversity and distribution patterns of corals in marginal environments, (2) investigate the diversity, distribution patterns and host specificity of symbionts in corals in marginal environments, (3) assess the influence of environmental variables on host and symbiont distribution in marginal environments, in comparison to 'optimal' environments, and (4) examine the physiological responses to changing environmental conditions and stress of corals and their symbionts in marginal environments. Surveys of coral community patterns were conducted at the Kermadec Islands (KI), New Zealand, and Palmyra Atoll, USA, with local scale environmental parameters (i.e. wave exposure and sedimentation) found to control the diversity and distribution of the coral communities. Symbiodinium types were identified to subcladal level in a range of coral species at each of the survey sites, using ITS2-DGGE. A high diversity of C type symbionts (19 types in 13 host genera), and reduced host specificity was observed at the high latitude site of Lord Howe Island (LHI), Australia, with similarly high diversity at the KI (10 types in 9 genera). Thirteen novel clade C types were identified in corals at LHI, with two of these types also present in hosts at the KI. The reduced host specificity of symbionts at LHI, compared to tropical sites, implies that the evolution of novel holobionts may be an important mechanism whereby corals can cope with variable and stressful conditions. Further, physiological assessment of the novel LHI symbionts led to the suggestion that Symbiodinium at LHI may be specialised for cooler and more variable temperatures, so contributing to the success of corals at this marginal location. In contrast, a low diversity of generalist symbionts (C and D types) were uncovered at the equatorial site of Palmyra Atoll (10 types in 13 genera), attributed to the stressful environmental regime resulting in a reduced population of stresstolerant symbionts. The variation in environmental parameters, particularly sedimentation, around Palmyra Atoll has led to diversification of coral communities, however this environmental variation has not affected the symbiont communities. While it has been suggested that marginal coral communities might be better adapted for survival in an environment modified by global climate change, the local scale environmental factors are also important drivers of both coral and symbiont distributions, and should be considered when making predictions for the future. Further, assessment of the physiological tolerance ranges of both the multiple, novel symbionts at high latitudes, and the few, potentially stress-tolerant symbionts at Palmyra should be conducted, to help determine whether they have the ability to adjust to new environmental conditions.</p>

Persistence of Corals in Marginal Habitats: the Role of the Environment, and Symbiont Diversity and Ecophysiology

<p>Many corals live in marginal habitats, close to their survival thresholds of water temperature, light penetration and aragonite saturation. Living under these highly variable and extreme conditions is likely facilitated by specific physiological adaptations and/or the presence of unique species of coral and their symbionts but data on these factors are limited. The specific objectives of the study were to: (1) examine the diversity and distribution patterns of corals in marginal environments, (2) investigate the diversity, distribution patterns and host specificity of symbionts in corals in marginal environments, (3) assess the influence of environmental variables on host and symbiont distribution in marginal environments, in comparison to 'optimal' environments, and (4) examine the physiological responses to changing environmental conditions and stress of corals and their symbionts in marginal environments. Surveys of coral community patterns were conducted at the Kermadec Islands (KI), New Zealand, and Palmyra Atoll, USA, with local scale environmental parameters (i.e. wave exposure and sedimentation) found to control the diversity and distribution of the coral communities. Symbiodinium types were identified to subcladal level in a range of coral species at each of the survey sites, using ITS2-DGGE. A high diversity of C type symbionts (19 types in 13 host genera), and reduced host specificity was observed at the high latitude site of Lord Howe Island (LHI), Australia, with similarly high diversity at the KI (10 types in 9 genera). Thirteen novel clade C types were identified in corals at LHI, with two of these types also present in hosts at the KI. The reduced host specificity of symbionts at LHI, compared to tropical sites, implies that the evolution of novel holobionts may be an important mechanism whereby corals can cope with variable and stressful conditions. Further, physiological assessment of the novel LHI symbionts led to the suggestion that Symbiodinium at LHI may be specialised for cooler and more variable temperatures, so contributing to the success of corals at this marginal location. In contrast, a low diversity of generalist symbionts (C and D types) were uncovered at the equatorial site of Palmyra Atoll (10 types in 13 genera), attributed to the stressful environmental regime resulting in a reduced population of stresstolerant symbionts. The variation in environmental parameters, particularly sedimentation, around Palmyra Atoll has led to diversification of coral communities, however this environmental variation has not affected the symbiont communities. While it has been suggested that marginal coral communities might be better adapted for survival in an environment modified by global climate change, the local scale environmental factors are also important drivers of both coral and symbiont distributions, and should be considered when making predictions for the future. Further, assessment of the physiological tolerance ranges of both the multiple, novel symbionts at high latitudes, and the few, potentially stress-tolerant symbionts at Palmyra should be conducted, to help determine whether they have the ability to adjust to new environmental conditions.</p>

Two new marine cyclopinids (Crustacea: Copepoda: Cyclopoida) from interstitial habitats in Korea

Marine cyclopoids, and especially cyclopinids, are poorly studied because their diversity is highest in marginal habitats, such as intertidal interstitial and anchialine caves, or in highly inaccessible abyssal and hadal depths. Two new cyclopinids are described here, both from two different sandy beaches in Korea. Among four species currently recognized in the genus, Heterocyclopina koreaensis sp. nov. is most closely related to H. vietnamensis Pleşa, 1969 from similar habitats in Vietnam. Koreacyclopina wellsi gen. et sp. nov. shares its sexually dimorphic third exopodal segment of the second leg with the Antarctic genus Pseudocyclopina Lang, 1946, but differs from all six known species by numerous features, some of which are observed for the first time within cyclopinids. Both Korean species belong to the family Hemicyclopinidae, but the monophyly of this group has not yet been demonstrated.

Physiological responses of scleractinian corals in marginal habitat

Polapa FS, Werorilangi S, Ali SM, Jompa J. 2021. Physiological responses of scleractinian corals in marginal habitat. Biodiversitas 22: 4011-4018. This study aims to analyze physiological differences in corals in marginal habitats. Under different conditions, the production/respiration (P/R) ratio and photobiology of various coral genera were compared. Samples were taken from three coral reef zones representing typical reef habitats and from the mangrove ecosystem as a marginal habitat. Surveys revealed two coral genera surviving in extreme conditions (marginal habitat). The P/R ratio measurements indicated that corals living in the mangrove ecosystem tend to be heterotrophic. This was supported by observations of colonies with tentacles extended from the corallites. Furthermore, Porites living in the mangrove habitat consume more O2 directly than saving it for other purposes, such as growth. The genus Dipsastraea exhibited elevated zooxanthellae density in the mangrove ecosystem, whereas Porites exhibited similar densities in both ecosystems.

Pueraria montana var. lobata (kudzu).

P. montana, formerly known as P. lobata, is widely known in the USA as 'kudzu' is native to East Asia. However, it does not appear to be a significant problem anywhere except in south-eastern USA where it was extensively planted in the 1930s and 1940s for erosion control. Seed dispersal appears to be minor but vegetative growth in subtropical areas can be substantial, up to 18 m per growing season. It is a climbing vine and kills vegetation by completely smothering it, and it will also entirely cover telegraph poles and buildings if left to itself. Once introduced it is difficult to control, especially in forest and marginal habitats. There are three varieties, although only var. lobata is so far known to be invasive, in the USA.

Age structure of a lizard along an elevational gradient reveals nonlinear lifespan patterns with altitude

Lifespan is one of the main components of life history. Shorter lifespans can be expected in marginal habitats. However, in the case of ectotherms, lifespan typically increases with altitude, even though temperature—one of the main factors to determine ectotherms’ life history—declines with elevation. This pattern can be explained by the fact that a shorter activity time favors survival. In this study, we analyzed how lifespan and other life-history traits of the lizard Psammodromus algirus vary along a 2,200 m elevational gradient in Sierra Nevada (SE Spain). Populations at intermediate altitudes (1,200–1,700 m), corresponding to the optimal habitat for this species, had the shortest lifespans, whereas populations inhabiting marginal habitats (at both low and at high altitudes) lived longest. Therefore, this lizard did not follow the typical pattern of ectotherms, as it also lived longer at the lower limit of its distribution, nor did it show a longer lifespan in areas with optimal habitats. These results might be explained by a complex combination of different gradients along the mountain, namely that activity time decreases with altitude whereas food availability increases. This could explain why lifespan was maximum at both high (limited activity time) and low (limited food availability) altitudes, resulting in similar lifespans in areas with contrasting environmental conditions. Our findings also indicated that reproductive investment and body condition increase with elevation, suggesting that alpine populations are locally adapted.