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1.
Here we provide evidence that confinement in Robinson Crusoe Island (located about 660 km west of continental Chile) over evolutionary time leads to strong morphological modifications in diving beetle (Dytiscidae) larvae. We analysed a large set of morphological larval characters for all currently recognised genera of Colymbetinae as a framework, to infer phylogenetic relationships within the large genus Rhantus Dejean, 1833 and, in particular, of the charismatic Juan Fernández diving beetle, Rhantus selkirki Jäch, Balke & Michat, 2015, comparing our results with a recent phylogeny of the Colymbetinae based on DNA sequence data. We suggest that adaptation to the island's particular habitats resulted in the reversal of certain characters of R. selkirki back to the plesiomorphic states. This may cause the species to be erroneously interpreted as more ‘primitive’ if only morphological characters are analysed. Confinement in the particular, shallow and barely vegetated aquatic habitats of Robinson Crusoe Island for a long time seems to have led to this divergent morphology, particularly in characters related to swimming ability such as several leg and urogomphal setae. In this way, R. selkirki larvae secondarily resemble those of some earlier diverging dytiscid lineages such as Agabinae and Copelatinae, which typically creep on the bottom of water bodies and do not swim well.  相似文献   

2.
The genus R haphithamnus (Verbenaceae) consists of two species, one in South America and another endemic to the Juan Fernández archipelago, Chile. The genus represents an example of anagenetic speciation in which the island populations have diverged from their colonizing ancestors to the point where they are recognized as a distinct species. The island species R haphithamnus venustus differs from the continental R . spinosus primarily by floral traits associated with adaptation to hummingbird pollination. Two molecular markers, amplified fragment length polymorphisms (AFLPs) and microsatellites, were used to estimate divergence between the continental and insular species, and to compare diversity in the two species. The comparable or greater diversity in the insular species observed in some diversity indices of AFLPs would support the hypothesis that during the course of anagenetic speciation it has recovered from any reduction of genetic diversity associated with colonization of the archipelago. This pattern of comparable or higher diversity in insular species is seen with other instances of anagenetic speciation in the Juan Fernández archipelago. By contrast, the lower genetic diversity in the insular R . venustus found in microsatellites is likely to be the result of a founder effect from the original colonization of the archipelago; prior molecular studies suggest recent colonization of the Juan Fernández archipelago by R haphithamnus . The seeming non‐concordance between the present results and the widely accepted biogeography of R haphithamnus inferred from other data is discussed and an explanation is presented.  相似文献   

3.
Notes on the Poaceae of the Robinson Crusoe (Juan Fernández) Islands, Chile, Brittonia 54: 154–163. 2001.—Poaceae in the Robinson Crusoe (=Juan Fernández) Islands number 53 species in 32 genera, of which 9% of the species are endemic, 9% indigenous, and 81% adventitious. The endemic taxa (and their conservation status) are:Agrostis masafuerana (rare),Chusquea fernandeziana (not endangered),Megalachne berteroana (not endangered),M. masafuerana (not endangered), andPodophorus bromoides (extinct).Megalachne andPodophorus are endemic genera. Comparisons with Poaceae in the Bonin and Volcano Islands, Canary Islands, Galápagos Islands, and Hawaiian Islands show different levels of endemism: number of endemic taxa, respectively, 5, 10, 12, 40; percent specific endemism, 8, 6, 21, 19. No endemic genera occur.Anthoxanthum odoratum, Avena barbata andHordeum murinum are noxious weeds in the Robinson Crusoe Islands. Many adventives are shared among floras of the archipelagos, with the highest ties of Robinson Crusoe being to the Canaries (53% of total Poaceae known in Juan Fernández) and the Hawaiian Islands (47%). Low levels of adventives occur within the Bonin (5%) and Galápagos (7%) Islands. In contrast, there are many endemic genera of Asteraceae in these same archipelagos: Bonin and Volcano Islands (1), Canary Islands (8), Galápagos Islands (5), and Hawaiian Islands (6); percent of specific endemism is also higher (20, 53, 54 and 56, respectively). Hypotheses for greater levels of endemics among oceanic island Asteraceae include more efficient dispersal mechanisms by wind and birds, animal pollination systems that result in greater degrees of geographic populational genetic isolation, and a vascular cambium that offers enhanced growth-form evolutionary opportunities.  相似文献   

4.
A first study of the ants on the three main islands of the Juan Fernández Archipelago (Chile) has revealed the presence of just three species, Hypoponera confinis, Linepithema humile, and Tetramorium bicarinatum, all widely distributed invasive species. Most notable among them is the Argentine ant, L. humile, an ecologically destructive species that has established several populations and appears to be expanding.  相似文献   

5.
Phylogenetic relationships were reconstructed among chironemid fishes based on morphological and molecular (lrRNA, NADH4, S7 ribosomal protein) characters. Two sympatric species from Juan Fernández in the southeast Pacific are not sister taxa, but rather exhibit independent relationships to Australian/New Zealand chironemids. The most plausible explanation for these relationships and contemporary distributions is an Australian/New Zealand origin of the family, followed by two trans-Pacific dispersal and colonization events, facilitated by larval entrapment within the West Wind Drift. This study demonstrates that the diversity of taxa on an island can reflect multiple colonizations, rather than in situ diversification, even in the case of very small, isolated, and geologically recent islands. When taken in conjunction with studies of related taxa, our results indicate that transoceanic dispersal of temperate cirrhitoid fishes in the South Pacific has been frequent and unidirectional. Molecular estimates of divergence time between southeast Pacific chironemids and their western relatives predate the emergence of Juan Fernández, consistent with hypotheses that much of the marine nearshore faunas of young southeast Pacific islands may be the product of successive transfer from older, now submerged islands.  相似文献   

6.
We compared the geographic distribution of groups of chondrychthid fishes of two physically proximal, although geographically different, regions that include the Juan Fernández seamounts and the central Chilean continental slope, both sampled at mesopelagic and mesobenthonic depths. The ridge is in the Nazca Plate, while the slope region in on the South American Plate, and is closer to the South American continent. We found six species of Chondrichthyes for the seamounts (four orders, four families). The slope sampling produced ten species of Chondrichthyes, of which Torpedo tremens De Buen 1959, was the only species in common with the Juan Fernandez area. There are clear differences between the Chondrichthyes of the two regions. These fisheries require adequate administrative modes.  相似文献   

7.
A new genus and species of Seuratiinae is described based on adults recovered from the Juan Fernández and Kermedec Petrels (Pterodroma externa and P. neglecta) from the Juan Fernández Islands of Chile (south Pacific). Navonia pterodromae n. gen., n. sp. is distinguished from the other genera and species in Seuratiinae by the combination of the following characters: (1) cordons arising from commissures of buccal lips originating a finely denticulate collarette divided into 2 lateral lobes, and detached from underlying cuticle; (2) inconspicuous simple to bicuspid deirids; (3) presence of area rugosa; and (4) presence of a large left spicule in the male. It is also distinguished from some genera and species in this subfamily by the presence of a lateral furrow. Seuratia shipleyi was also recorded from P. externa. These are the first records of helminths in these 2 hosts and the first records of Seuratiinae from Chile.  相似文献   

8.
Records of derogenid digeneans in the Mediterranean and Black Sea region are scarce and tend to be restricted to a small number of host-groups, but especially to sparid fishes. This work reports on the presence of derogenine and halipegine derogenids from two sparids, Diplodus annularis (L.) and D. sargus (L.), from off the Mediterranean coast of Spain. Five derogenid forms were recovered. Derogenes adriaticus Nikolaeva, 1966 is redescribed from Diplodus annularis, and Derogenes sp. is described from the same host but differentiated from the former species. Magnibursatus barretti n. sp. is described from Diplodus sargus and distinguished from other species of the genus especially by its smaller body size and smaller eggs. M. bartolii Kostadinova, Power, Fernández, Balbuena, Raga & Gibson, 2003 is redescribed from D. sargus, a new host for this species. A single specimen from D. sargus, somewhat similar to M. minutus Kostadinova, Power, Fernández, Balbuena, Raga & Gibson, 2003, is also described, as it exhibits some morphometric differences from the latter species.  相似文献   

9.
Hahn  Ingo  Vergara  Pablo M.  Baumeister  Julia  Soto  Gerardo E.  Römer  Uwe 《Population Ecology》2015,57(1):143-149
It is a long-standing question how tsunamis can influence wild populations of animals and plants. Here, we assessed short-term changes in the population of the critically endangered Juan Fernández Firecrown (Sephanoides fernandensis) by using abundance data recorded 1 year before and 1 year after the 2010 Chilean tsunami. We tested that the abundance of Firecrowns declined in the areas where the tsunami caused the massive loss of Cabbage Trees, an important seasonal nectar source for Firecrowns. The abundance of Juan Fernández Firecrowns decreased after the tsunami, but also was affected by the habitat type, altitude, and the abundance of Cabbage Trees. Firecrowns tended to be more abundant in settlement areas than in native forest whereas the reduction in Firecrown abundance after the tsunami was more intense in settlement areas than in native forest. As expected, this habitat effect was dependent on the massive loss of Cabbage Trees in settlement areas following the tsunami. In spite of the short-term nature of our data, our results are conclusive in showing that the loss of an important food source causes short-term changes in the distribution and abundance of Firecrowns, which, in turn, could contribute to population decline.  相似文献   

10.
Myrceugenia is a mainly temperate South American genus with two species on the Juan Fernández Islands, 12 in central and southern Chile and adjacent Argentina, and 25 in the highlands of southeastern Brazil and adjacent regions. The continental populations are separated by about 1000 km. Numerical cladistic procedures based on the criteria of parsimony, compatible characters and a combination of compatible characters and character correlation are used to deduce hypothetical phylogenetic undirected trees. These indicate that 3–8 groups of species bridge the continent of South America. An explanation of how the distribution of the genus could have come about is given based on: 1) the above mentioned numerical analyses, 2) the ecology of the species, 3) the distribution of other plant genera, and 4) theories of the geologic and climatic history of southern South America. Myrceugenia is hypothesized to have grown continuously across South America during the early Tertiary and to have become divided into eastern and western populations probably during the Miocene.  相似文献   

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