Hawksbill turtle terra incognita: conservation genetics of?eastern Pacific rookeries

Prior to 2008 and the discovery of several important hawksbill turtle (Eretmochelys imbricata) nesting colonies in the EP (Eastern Pacific), the species was considered virtually absent from the region. Research since that time has yielded new insights into EP hawksbills, salient among them being the use of mangrove estuaries for nesting. These recent revelations have raised interest in the genetic characterization of hawksbills in the EP, studies of which have remained lacking to date. Between 2008 and 2014, we collected tissue samples from 269 nesting hawksbills at nine rookeries across the EP and used mitochondrial DNA sequences (766 bp) to generate the first genetic characterization of rookeries in the region. Our results inform genetic diversity, population differentiation, and phylogeography of the species. Hawksbills in the EP demonstrate low genetic diversity: We identified a total of only seven haplotypes across the region, including five new and two previously identified nesting haplotypes (pooled frequencies of 58.4% and 41.6%, respectively), the former only evident in Central American rookeries. Despite low genetic diversity, we found strong stock structure between the four principal rookeries, suggesting the existence of multiple populations and warranting their recognition as distinct management units. Furthermore, haplotypes EiIP106 and EiIP108 are unique to hawksbills that nest in mangrove estuaries, a behavior found only in hawksbills along Pacific Central America. The detected genetic differentiation supports the existence of a novel mangrove estuary “reproductive ecotype” that may warrant additional conservation attention. From a phylogeographic perspective, our research indicates hawksbills colonized the EP via the Indo‐Pacific, and do not represent relict populations isolated from the Atlantic by the rising of the Panama Isthmus. Low overall genetic diversity in the EP is likely the combined result of few rookeries, extremely small reproductive populations and evolutionarily recent colonization events. Additional research with larger sample sizes and variable markers will help further genetic understanding of hawksbill turtles in the EP.     

几种高等水生植物的克藻效应

研究了水花生、水浮莲、满江红、紫萍、浮萍和西洋菜对雷氏衣藻的相生相克关系,并和水葫芦的作用进行了比较。试验指出前五种水生植物对雷氏衣藻表现了克制作用,但它们的克藻效能不如水葫芦强。西洋菜没有克制作用,甚至稍有促进效应。从水花生、水浮莲、水葫芦的种植水中得到的分泌物粗提物,都显示了对雷氏衣藻的抑制效应,进一步证实了有相生相克关系的存在。试验结果说明高等水生植物对藻类的克制作用似有一定的普遍性,在水生生态系统的形成和演替过程中可能起着重要的作用。     

Coastal insect herbivore communities are affected more by local environmental conditions than by plant genotype

Abstract.

• 1 We compared the effects of plant genotype and local environment on population densities of a community of coastal insect herbivores in west-central Florida. Reciprocal transplants of four genotypes of three species of coastal plants, Borrichia frutescens, Iva frutescens and Limbricata, were made in July 1992 between a series of off-shore islands.
• 2 For each plant species, phytophagous insects with a wide range of feeding modes including gall-makers, stem borers, leaf miners and sap suckers were affected more by local environment than by plant genotype. Whereas host genotype had a significant effect on the population densities of gall-makers on B.frutescens in the spring of 1993, no significant effect on the denrities of any other insect species was found and the effect on the gall-makers on Borrichia disappeared in the summer, 1 year after the transplants had been made. In our study, local environment had by far the greatest effect on insect population densities among islands. This is an unusual result because in other studies over 80% of the insect species examined have been affected by plant genotype (Karban, 1992). This result is consistent with that reported by Stiling (1994), who censused populations of two phytophagous insects on reciprocal transplantr ot Borrichia in north Florida.
• 3 Local environment also had an effect on insect population densities within islands. This result contrasts with similar studies performed in north Florida (Stiling, 1994), where population densities did not differ within areas, and underlies how some biotic processes may change with in the same community even over relatively small changes in species range.

     

玳瑁和绿海龟幼体外周血细胞的观察与比较

对玳瑁(Eretmochelys imbricata)和绿海龟(Chelonia mydas)外周血细胞形态特征及其数量进行了观察、测定与比较.结果表明,在2种海龟外周血都观察到7种血细胞:红细胞、淋巴细胞、单核细胞、嗜中性粒细胞、嗜酸性粒细胞、嗜碱性粒细胞和血栓细胞,除了绿海龟观察到大、小2种嗜酸性粒细胞外,另外几种血细胞的形态结构与其他爬行动物相似.白细胞分类计数表明,2种海龟白细胞中以嗜中性粒细胞数量最多,其次是淋巴细胞和单核细胞,嗜酸性粒细胞仅有少数,嗜碱性粒细胞极少,并且此类细胞在玳瑁的白细胞分类计数中为零.玳瑁红细胞数量为(346.7±68.4)×10~3个/μl,比绿海龟红细胞含量少,绿海龟为(403.3±170.6)×10~3/μl;玳瑁白细胞及血栓细胞数分别为(7.7±1.9)×10~3个/μl和(9.6±2.2)×10~3个/μl,绿海龟分别为(7.3±2.8)×10~3个/μl和(7.5±3.7) ×10~3个/μl.     

A Two Phase Photoperiodic Response Controlling the Annual Gametogenic Cycle in Harmothoe imbricata (L.) (Polychaeta: Polynoidae)

Summary

In the polychaete Harmothoe imbricata, a photoperiodic mechanism stabilises oogenesis during its early stages and prevents oocyte breakdown. During the autumn, photoperiods of 14 hr light per day or more cause the animals to abort gametogenesis and resorb their oocytes. Conversely, photoperiods of 13 hr or less stabilise gametogenesis and allow normal oocyte growth. The length of the exposure required to stabilise gametogenesis and prevent abortion lies between 42 and 55 days. This effect is in addition to a previously described phenomenon causing accelerated oocyte growth in the spring in response to moderately long photoperiods. The interaction between these two different photoperiodic responses is discussed.     

Príncipe island hawksbills: Genetic isolation of an eastern Atlantic stock

The hawksbill turtle is a critically endangered species that has been extensively exploited for centuries. Príncipe Island off western Africa harbours one of the species' major nesting populations in the eastern Atlantic, as well as hosting year-round foraging aggregations of juveniles, subadults and adult males. To gain insight into the population's genetic structure and relationships with regional stocks, we analysed mitochondrial DNA (mtDNA) sequences of nesting females (N = 9), foraging adult females (N = 11), adult males (N = 32), subadults (N = 15) and juveniles (N = 80). The nesting population was found to be fixed for a single haplotype (EATL), which had been previously reported in both western and eastern Atlantic hawksbill foraging sites but had no known rookery source prior to this study. Thus it is now possible to confirm the westward transoceanic movement by hawksbills originating from Príncipe Island. Our analyses demonstrated that the Príncipe Island nesting colony is genetically distinct from breeding populations in the western Atlantic and is phylogenetically linked with Indo-Pacific hawksbill clades, suggesting that Príncipe Island was most likely colonised by migrants from the Indian Ocean via the Cape of Good Hope in southern Africa. Mixed stock analyses revealed that the eastern Atlantic appears to be the primary foraging area for Príncipe hawksbills (75%) while most of the foraging juveniles in Príncipe waters originate from the Príncipe rookery (84%). Furthermore, the presence of Caribbean haplotypes at low frequencies (< 5%) suggests that eastward transatlantic movements by juveniles to distant foraging and developmental habitats also take place. Depleted hawksbill populations in the eastern Atlantic combined with the low genetic variability and high genetic distinctiveness found in the Príncipe nesting and foraging aggregations with respect to the western Atlantic, underscore the high degree of isolation and vulnerability of this eastern Atlantic stock. These characteristics are highly relevant for the development of effective conservation programmes and highlight the urgent need to consolidate international cooperation across regional boundaries.     

New red alga Meristotheca imbricata (Solieriaceae, Gigartinales) from Japan

A new red alga Meristotheca imbricata Faye et Masuda (Solieriaceae, Gigartinales) was described on the basis of specimens collected from southern Japan. Although this species might have been for a long time included in the concept of M. coacta Okamura, until recently a very poorly known alga, it is distinguished from the latter by the following features: (i) each thallus consists of one primary blade and several secondary blades, the latter arising from the apical or subapical portion of terminal segments of the primary blade; (ii) the individual blades are repeatedly dichotomously divided into linear segments of which margins are neither undulate nor crispate, and are fleshy, imbricate, frequently anastomosing and often acervate; (iii) each tetrasporangial initial is attached by a basal pit-connection to the parental cell, and the position of the pit-connection changes from basal to lateral by inward growth of the tetrasporangium; and (iv) the carpogonial branches sometimes have a one-celled sterile lateral.     

Evidence of opposing fitness effects of parental heterozygosity and relatedness in a critically endangered marine turtle?

How individual genetic variability relates to fitness is important in understanding evolution and the processes affecting populations of conservation concern. Heterozygosity–fitness correlations (HFCs) have been widely used to study this link in wild populations, where key parameters that affect both variability and fitness, such as inbreeding, can be difficult to measure. We used estimates of parental heterozygosity and genetic similarity (‘relatedness’) derived from 32 microsatellite markers to explore the relationship between genetic variability and fitness in a population of the critically endangered hawksbill turtle, Eretmochelys imbricata. We found no effect of maternal MLH (multilocus heterozygosity) on clutch size or egg success rate, and no single‐locus effects. However, we found effects of paternal MLH and parental relatedness on egg success rate that interacted in a way that may result in both positive and negative effects of genetic variability. Multicollinearity in these tests was within safe limits, and null simulations suggested that the effect was not an artefact of using paternal genotypes reconstructed from large samples of offspring. Our results could imply a tension between inbreeding and outbreeding depression in this system, which is biologically feasible in turtles: female‐biased natal philopatry may elevate inbreeding risk and local adaptation, and both processes may be disrupted by male‐biased dispersal. Although this conclusion should be treated with caution due to a lack of significant identity disequilibrium, our study shows the importance of considering both positive and negative effects when assessing how variation in genetic variability affects fitness in wild systems.