Content uploaded by Francis Howarth
Author content
All content in this area was uploaded by Francis Howarth on Oct 05, 2014
Content may be subject to copyright.
Bioclimatic and geologic factors governing the evolution and distribution of Hawaiian cave insects. Entomol Gen 8:17-26
... However, the spaces that form the principal habitat of most troglobites are probably larger than 10 mm in width. Below the soil layer these occur most often in soluble and volcanic terrains, and occasionally in other rock types or rocky deposits (68,69,78,79,160). These mesocavernous voids are generally too large for the smaller soil invertebrates to negotiate, especially if there are wet vertical walls or pools of water (23,25). ...
... First, the entrance zone is often richer than either the cave or surface habitats (66) and second, most surface species cannot cope with the rigors of the cave (14, 23, 25, 26, 67-69, 120, 135, 146). Troglobites are restricted to the deep cave zone, and the most critical environmental factor governing their distribution appears to be the stable saturated atmosphere (65,69). The boundary of the deep zone may be defined by the negligible potential evaporation rate (8,21,65,69). ...
... Troglobites are restricted to the deep cave zone, and the most critical environmental factor governing their distribution appears to be the stable saturated atmosphere (65,69). The boundary of the deep zone may be defined by the negligible potential evaporation rate (8,21,65,69). Many troglobites migrate closer to the entrance, even into the twilight zone, during wetter periods and further into the cave as the passages dry out (6,8,69). ...
Cavernicoles can be divided into 1) troglobites - obligate cave-dwellers that cannot survive outside the hypogean environment; 2) troglophiles - facultative species that live and reproduce in caves but which are found in similar dark, humid microhabitats on the surface; and 3) trogloxenes - which regularly inhabit caves for refuge but normally return to the surface to feed. Following brief comments on zoogeography, discussion centres on the nature of the subterranean biome, energy sources in caves, nutrient cycling, and behavioural responses by the arthropods. Notes are also provided on experimental work, and the need for conservation is indicated. -P.J.Jarvis
... By far, however, the most studied lava tube fauna in the United States occurs in Hawaii. Many authors cover various systematic groups in detail (Barnard 1977, Bellinger and Christiansen 1974, Brindle 1980, Bousfield and Howard 1976, Fennah 1973, Gagné and Howarth 1975aand 1975b, Gertsch 1973, Gurney and Rentz 1978, Hoch 2002, Liebherr and Samuelson 1992, Muchmore 1979, Schultz 1973, Wirth and Howarth 1982, Zacharda 1982 and Howarth (1981Howarth ( , 1982Howarth ( , 1987aHowarth ( , 1987bHowarth ( , 1991 analyzed the ecology and evolution of various taxa. ...
From Abstracts of the 2006 National Speleological Society Convention, 7-11 Aug 2006, Bellingham, WA (USA)
... The first four of these groups also appear to dominate clone libraries from the subsurface microbial mats. Because of the lack of sunlight beyond the Twilight Zone (Howarth, 1982), Cyanobacteria are rarely found in caves except for this zone (Martinez and Asencio, 2010). Studies of soils, in general, have found that soils are dominated by Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia, Bacteroidetes, Chloroflexi, Planctomycetes, Gemmatimonadetes, and Firmicutes ( Janssen, 2006). ...
Lava caves contain a wealth of yellow, white, pink, tan, and gold-colored microbial mats; but in addition to these clearly biological mats, there are many secondary mineral deposits that are nonbiological in appearance. Secondary mineral deposits examined include an amorphous copper-silicate deposit (Hawai'i) that is blue-green in color and contains reticulated and fuzzy filament morphologies. In the Azores, lava tubes contain iron-oxide formations, a soft ooze-like coating, and pink hexagons on basaltic glass, while gold-colored deposits are found in lava caves in New Mexico and Hawai'i. A combination of scanning electron microscopy (SEM) and molecular techniques was used to analyze these communities. Molecular analyses of the microbial mats and secondary mineral deposits revealed a community that contains 14 phyla of bacteria across three locations: the Azores, New Mexico, and Hawai'i. Similarities exist between bacterial phyla found in microbial mats and secondary minerals, but marked differences also occur, such as the lack of Actinobacteria in two-thirds of the secondary mineral deposits. The discovery that such deposits contain abundant life can help guide our detection of life on extraterrestrial bodies.
When you enter a cave, as a human, you are immediately struck by what an alien environment you have entered, as the light fades, and cool, moist air surrounds you. Using artificial light to illuminate your journey through this rock-dominated environment, you may think that nothing lives here, but biologists and microbiologists have been discovering a wealth of life in these rock chambers beneath the Earth’s surface. And, now, a new revolution is taking place in how we view caves—scientists are discovering that these environments are home to organisms that produce secondary metabolites that may be useful to humans. But, what shapes this production and the microorganisms that produce these compounds? That is the focus of this chapter. We’ll start with some background on caves in general, move to the abiotic factors that characterize caves, provide selective pressures for microbial evolution, and then review what energy sources fuel microbial growth and existence in caves, look at why caves make such ideal laboratories, and end with the significance of studying microbial life in caves, including secondary metabolite production, geomicrobiology, and relevance to life detection on extraterrestrial bodies.
Eight species of Collembola are reported from recent collections made in caves on the Polynesian island of Rapa Nui (Eas-ter Island). Five of these species are new to science and apparently endemic to the island: Coecobrya aitorererere n. sp., Cyphoderus manuneru n. sp., Entomobrya manuhoko n. sp., Pseudosinella hahoteana n. sp. and Seira manukio n. sp. The Hawaiian species Lepidocyrtus olena Christiansen & Bellinger and the cosmopolitan species Folsomia candida Wil-lem also were collected from one or more caves. Coecobrya kennethi Jordana & Baquero, recently described from Rapa Nui and identified as endemic, was collected in sympatric association with C. aitorererere n.sp. With the exception of F. candida, all species are endemic to Rapa Nui or greater Polynesia and appear to be restricted to the cave environment on Rapa Nui. A key is provided to separate Collembola species reported from Rapa Nui. We provide recommendations to aid in the conservation and management of these new Collembola, as well as the other presumed cave-restricted arthropods.
Australia, including the tropical north, is currently recognized as having one of the world's richest underground faunas. Until fairly recently, it was widely believed that cave adapted species (troglobites) did not exist in the tropics. Lava tubes were also considered to be devoid of troglobites, and the Australian continent was thought to have relatively few cave adapted species due to its aridity. Leleup in the Galapagos in 1968, Howarth in Hawai'i in 1971, and subsequent researchers discovered numerous troglobites in lava tubes on volcanic islands in the tropical Pacific. Based on his work in Hawai'i, Howarth developed a bioclimatic model including the "tropical winter" effect to explain the restriction of troglobites to deep cave zones and small subsurface voids (mesocaverns) with constant high humidity. Brother Nicholas Sullivan, with the Sydney Speleological Society and the Chillagoe Caving Club, began to survey the biology of the Chillagoe limestone caves and in 1984 invited Francis Howarth and Fred Stone to join the 1984 to 1986 expeditions with support from The Explorers Club. During the 1984 expedition, they learned of Anne Atkinson's detailed studies of a number of lava tubes in the McBride Volcanic Province at Undara and in 1985, guided by Douglas Irvin of the Chillagoe Caving Club, they went to investigate. With enthusiastic support of the Pinwill family, who held the grazing lease, they were able to enter many of the lava tubes at Undara and on the neighbouring cattle stations managed by the Collins brothers. Bayliss lava tube had an ideal conformation to foster a stable, humid deep cave climate, with a restricted entrance, a sealed back end, and barriers to air circulation plus abundant food supplies from bat guano and tree roots. Two dozen previously unknown cave adapted species were discovered. An additional feature was a high level of carbon dioxide in the deep cave where troglobites were the most abundant. This combination of high humidity and carbon dioxide makes Bayliss lava tube a "window" into the much broader mesocavernous zone. Other lava tubes in the McBride Province with similar conditions were found to have several additional troglobitic species. These discoveries complemented the work on tropical volcanic islands by showing that tropical continental lava tubes were also rich in troglobitic species. Comparisons between the old Chillagoe limestone caves and relatively young (190,000 year old) lava tubes confirmed the bioclimatic model. Subsequent work across Australia by Humphreys, Clarke, Eberhard and numerous others has resulted in discovery of subterranean "hot spots" in other geologic formations in which caves and/or mesocaverns occur. Where these formations lack caves, well bores and mining test bores are being sampled with bait traps. Other Australian volcanic areas, such as Black Braes, show high potential for cave species, and where lava tubes are lacking well bore sampling could reveal their mesocavernous fauna.
The Australian genus Solonaima comprises thirteen described plus two undescribed species. Six are cavernicolous, obligate or not, and are found in different caves. The phylogeny presented here confirms the monophyly of the genus. This phylogeny was compared with the estimate obtained using the method of Marques and Gnaspini, who recommend coding characters susceptible to parallelism differently from the others. Further comparison was made with a cladogram derived from the matrix from which such characters susceptible to parallelism were withdrawn. Scenarios concerning historical invasions of caves were tested using phylogenetic inference. The most‐parsimonious hypothesis proposed four invasions of the caves, within two of which a diversification of species took place.
Lava tube caves in the Hawaiian Islands contain an impressive array of troglobitic arthropod species. These animals exhibit striking morphological adaptations to their subterranean environment including loss of eyes and body pigment, reduction or elimination of wings, and hypertrophication of chemosensory and tactile organs. Certain modifications of water balance and metabolic rates are also apparent in these cave-adapted animals.
Neither Hawaiian troglobites nor their surface relatives can absorb water vapor from a saturated atmosphere even following a period of prolonged desiccation, whereas both forms are able to restore water deficits adequately through drinking. Lava tube crickets (34.5 and 52.3 μg cm−2 hour−1 mmHg−1) and spiders (33.4 μg cm−2 hour−1 mmHg−1) possess greater integumentary permeabilities than their epigean relatives (crickets, 26.2; spiders, 3.1 μg cm−2 hour−1 mmHg−1).
Hawaiian troglobitic crickets lack a diel metabolic rate (night = 279.5 ± 20.1; day = 280.8 ± 13.5 μl 02 gm−1 hour−1). The daily average metabolic rates of cave-adapted (280.2 ± 15.3) and surface crickets (277.4 ± 9.8 μl 02 gm−1 hour−1) are not significantly different (P > 0.05), however, suggesting differential strategies of caloric utilization in the two environments which may be related to water availability.
Tropical troglobites are unlikely to have evolved from troglophiles isolated by climatic extremes, because the latter were not subjected to the severe temperatures that their temperate counterparts endured during the Pleistocene. If pre-adapted forms enter tropical caves directly and undergo adaptive shifts, it is possible that they do so in search of a moist substrate. the present study is the first field test of this hypothesis. the preference of the tropical troglophile Paratemnopteryx sp. (Blattodea: Blattellidae) for moist leaves compared with dry leaves was studied in a tropical cave. the relative attractiveness of leaves in leaf litter traps was compared at a range of different relative humidities in the cave. the relative attractiveness of wet leaves was found to increase as the cave atmosphere became progressively drier towards the cave entrance. I suggest that some tropical troglophiles seek the wet leaf litter available in caves, and that they may remain in deep caves which provide this resource without climatic isolation events keeping them there. This finding lends empirical support to the idea that many species from the great variety of tropical organisms invade caves, resulting in what has recently been shown to be a tropical cave fauna relatively rich in troglobites.
ResearchGate has not been able to resolve any references for this publication.