Evolution and adaptations of Galapagos sea-birds

With two endemic genera, 26% endemism at the specific, and 58% endemism at the subspecific level, the Galapagos sea-bird fauna is more highly endemic than that of any other archipelago. Of the four most distinct, hence probably oldest, endemics, three are probably of north Pacific origin and the fourth may be. The next most distinct group is of Humboldt Current origin, and the remainder, which are very little differentiated, are of Pacific or Caribbean origin. Special adaptations to Galapagos conditions include the loss of flight by a cormorant and the evolution of nocturnal habits by a gull, the latter probably as a result of kleptoparasitism or nest-predation by frigatebirds. As a group the Galapagos sea-birds show varied adaptive responses to the relatively ascasonal and highly unpredictable marine environment. Opportunistic and non-annual breeding regimes predominate. Unlike the Galapagos land-birds, the study of Galapagos sea-birds has thrown light not on speciation processes but on the consequences of natural selection acting on breeding ecology and associated behaviour.     

Seals of the Galapagos Islands

The Galapagos archipelago has been colonized by two species of otariid, the fur seal, Arctocephalus galapagoensis , and the sea lion, Zalophus californianus wollebaeki. The former probably arrived from South America and the latter from North America, both by way of periodic incursions of colder water forming the east Pacific corridor. The terrestrial behaviour of both these otariids is affected by the high ambient temperatures in the Galapagos Patterns of breeding behaviour of otariids which lead to intense polygyny and sexual dimorphism appear to be modified. The habit of prolonging lactation, widespread in otariids, is carried to an extreme in the Galapagos fur seal. The reason for this is unclear.     

Some Oceanographic Observations in the Galapagos Islands

The oceanographic conditions that obtained during the periodof study are described. The study area is characterized by surfacetemperatures near 20°C and a sharp thermocline at a depthof 40 m. The temperature below 1000 m is less than 5°C.An episode of upwelling occurred during the period of study.The upwelled water was displaced by water characteristic ofthat found north of the Equatorial Front. The approximate positionof the Equatorial Front during the study period was 00°15' S latitude.     

110 years of Avipoxvirus in the Galapagos Islands

The role of disease in regulating populations is controversial, partly owing to the absence of good disease records in historic wildlife populations. We examined birds collected in the Galapagos Islands between 1891 and 1906 that are currently held at the California Academy of Sciences and the Zoologisches Staatssammlung Muenchen, including 3973 specimens representing species from two well-studied families of endemic passerine birds: finches and mockingbirds. Beginning with samples collected in 1899, we observed cutaneous lesions consistent with Avipoxvirus on 226 (6.3%) specimens. Histopathology and viral genotyping of 59 candidate tissue samples from six islands showed that 21 (35.6%) were positive for Avipoxvirus, while alternative diagnoses for some of those testing negative by both methods were feather follicle cysts, non-specific dermatitis, or post mortem fungal colonization. Positive specimens were significantly nonrandomly distributed among islands both for mockingbirds (San Cristobal vs. Espanola, Santa Fe and Santa Cruz) and for finches (San Cristobal and Isabela vs. Santa Cruz and Floreana), and overall highly significantly distributed toward islands that were inhabited by humans (San Cristobal, Isabela, Floreana) vs. uninhabited at the time of collection (Santa Cruz, Santa Fe, Espanola), with only one positive individual on an uninhabited island. Eleven of the positive specimens sequenced successfully were identical at four diagnostic sites to the two canarypox variants previously described in contemporary Galapagos passerines. We conclude that this virus was introduced late in 1890's and was dispersed among islands by a variety of mechanisms, including regular human movements among colonized islands. At present, this disease represents an ongoing threat to the birds on the Galapagos Islands.     

Anchialine podocopid Ostracoda of the Galapagos Islands

Water-filled fissures and lava tubes on Isla Santa Cruz and Isla Isabela provide anchialine habitats for 11 species of podocopid and platycopid Ostracoda, most with Atlantic and West Indian affinities. Their ancestors may have been carried to earlier islands in the Galapagos system by trans-Isthmian currents, on vegetation or larger animals, or by migrating waterfowl. None are derived from present-day Pacific coastal faunas of North, Central or South America. Two species of Cytheracea, a new species of Anchistrocheles (Bairdiacea), and one of Cytherella (Platycopida) are described.     

Paleochemistry of manganese in corals from the Galapagos Islands

Approximately 550 measurements of Mn/Ca ratios in three corals from the western Galapagos Islands have been performed to reconstruct a 380-year history of surface ocean variability with respect to this trace element. The time period studied encompasses 1600 A.D. to 1978. Manganese is inferred to be lattice-bound in coralline aragonite at 10–50% of its seawater proportion to calcium; uncertainty about the distribution coefficient stems from inherent variability of oceanic Mn in nearshore settings. Interannual variations at Urvina Bay, Isabela Island are generally small, with the exception of a few decades during the nineteenth century. A large positive Mn/Ca anomaly found between 1821–1830 is hypothesized to have resulted from a major volcanic eruption on nearby Fernandina Island in 1825. On intrannual timescales a pronounced cycle occurs in response to seasonal upwelling. Quarterly changes in Mn/Ca are six months out-of-phase with Cd/Ca variations-a reflection of the opposite distributions of these metals in the upper waters of the eastern Pacific. High frequency reconstructions over brief time intervals from the 17th, 18th, and 20th century reveal that the seasonal onset of warm and cool phases near Galapagos has persisted for at least 340 years. A quantitative assessment of historical changes in upwelling intensity is complicated by offsets in background Mn levels recorded by different corals. One apparent longterm feature is an overall decline in skeletal Mn concentrations from 1600–1978 which results in a net decrease of 20–30%. Several possible explanations exist for this trend, ranging from accumulation of a persistent diagenetic Mn phase in fossil aragonite to a temporal shift in oceanic/atmospheric Mn fluxes reaching the surface waters of the Galapagos Islands.     

Marine Ostracoda of the Galapagos Islands and Ecuador

Marine algae collected from rock pools on Hood, Fernandina and Mosquera, in the Galapagos Islands, have provided a fauna of 26 ostracod species of which 14 are new. One genus, belonging to the Hemicytheridae, is also new and appears to be endemic to the Islands. From two littoral algal samples collected from Punta Canoa and San Pedro beach, Ecuador, an assemblage of some nine species, four of which are new, is also described. Two ostracods: Touroconcha lapidiscola and Loxoconcha (Lox-ocorniculum) lenticuloides , are the only species so far known to be present both in the Galapagos Islands and off the coast of Central and South America. One species: Cytherelloidea praecipua recorded from off Tobago and Clipperton Islands may be present in the Galapagos but this has not definitely been confirmed. The evolution in the Gulf Coast/Caribbean region of several ostracods and their subsequent dispersal westwards is discussed.     

Trichomonas gallinae in columbiform birds from the Galapagos Islands

Domestic pigeons were introduced into the Galapagos Islands in 1972 or 1973. There is a high prevalence of Trichomonas gallinae among them and some evidence of canker. Trichomonas gallinae can be found also in endemic Galapagos doves in the vicinity of Puerto Ayora on Santa Cruz Island. Doves examined on pigeon-free islands were not found infected.     

A summary of geographical characteristics of the Galapagos Islands

Republished here, with permission, in a slightly modified form, from Noticias de Galapagos 55, July 1995, 18–24. Copyright remains, by agreement, with Noticias de Galápagos , which is published by The Charles Darwin Foundation for the Galápagos Islands.     

Cuticular hydrocarbons of grasshoppers from the Galapagos Islands, Ecuador

Cuticular lipids of adult Schistocerca literosa, Schistocerca melanocera and Halmenus robustus were analyzed. They have a similar range of hydrocarbons to those previously reported for other grasshoppers, but contain significant amounts of squalene which has not previously been reported from grasshopper cuticle. In Halmenus, squalene comprises 17% of the total hydrocarbons, while internally branched methylalkanes are present in much smaller quantities than in other grasshoppers. The results lend no support for a close taxonomic link between Halmenus and Schistocerca.     

Amphipod crustaceans from anchihaline cave waters of the Galapagos Islands

Three species of blind Amphipoda are recorded from anchihaline cave waters in the Galapagos Islands. One of these, Galapsiellus leleuporum (Monod, 1970) was previously know from the islands; the male is described for the first time. The other two belong to families with predominantly (though not exclusively) deep-sea members: Valettietta cavernicola sp. nov. (family Lysianassidae; and Antronicippe serrata gen. et sp. nov. (family Pardaliscidae). The genus Valettietta was not previously recorded from caves; it contained two abyssal species in the Atlantic, while a third species was recorded from the Pacific in a vertical haul between 0 and 5300 m. Antronicippe is closely related to Spelaeonicippe , a genus with two species known from anchihaline caves in the Canary Islands and the West Indies.     

Amphipod crustaceans from anchihaline cave waters of the Galapagos Islands

Three species of blind Amphipoda are recorded from anchihaline cave waters in the Galapagos Islands. One of these, Galapsiellus leleuporum (Monod, 1970) was previously know from the islands; the male is described for the first time. The other two belong to families with predominantly (though not exclusively) deep-sea members: Valettietta cavernicola sp. nov. (family Lysianassidae; and Antronicippe serrata gen. et sp. nov. (family Pardaliscidae). The genus Valettietta was not previously recorded from caves; it contained two abyssal species in the Atlantic, while a third species was recorded from the Pacific in a vertical haul between 0 and 5300 m. Antronicippe is closely related to Spelaeonicippe, a genus with two species known from anchihaline caves in the Canary Islands and the West Indies.     

Species number,area and habitat diversity in the Galapagos Islands

The Galapagos vascular plant species are divided into two groups, showing preferences for dry and wet habitats. This division is based on the results of a phytosociological study and is not influenced by such factors as island area, elevation, climate or soil types. The different distribution patterns of the dry and wet species are discussed and it is concluded that habitat diversity offers a better explanation for species numbers and distribution patterns than do island size and isolation. Claims that a dynamic MacArthur-Wilson type equilibrium has been reached for vascular plants in the Galapagos archipelago seem premature.     

Spirorbinae (Polychaeta: Serpulidae) of the Galapagos Islands*

Twelve species, six of which are new, are recorded from shores andshallow water. The most generally abundant are Spirorbis tricornigerus Rioja, S. bushi Rioja (both dextral with tube incubation), S. regalis sp. n., S. tuberculatus sp. n. (both sinistral with opercular incubation) and S. placophora sp. n. (sinistral, with tube incubation). Other sinistral species include S. claparedei Caullery & Mesnil, S. berkeleyana Rioja, S. bidentatus sp. n., and S. translucens sp. n. Dextral species include S. marioni Caullery & Mesnil, S. pagenstecheri Quatrefages and S. unicornis sp. n. The new species mentioned above have been described by the author named first.
The Spirorbis fauna seems to be quite like that of Mexico and S. America, from which repeated introductions have probably occurred, perhaps on stones buoyed by seaweeds and drifting on the Peruvian and El Nino currents. Its considerable diversity is not attributed to speciation within the archipelago.     

The distribution of mosquitoes across an altitudinal gradient in the Galapagos Islands

An avian malaria parasite (genus Plasmodium) has been detected consistently in the Galapagos Penguin (Spheniscus mendiculus) and less frequently in some passerines. We sampled three resident mosquito species (Aedes taeniorhynchus, Culex quinquefasciatus, and Aedes aegypti) using CDC light and gravid traps on three islands in 2012, 2013, and 2014. We sampled along altitudinal gradients to ask whether there are mosquito‐free refugia at higher elevations as there are in Hawaii. We captured both Ae. taeniorhynchus and Cx. quinquefasciatus at all sites. However, abundances differed across islands and years and declined significantly with elevation. Aedes aegypti were scarce and limited to areas of human inhabitation. These results were corroborated by two negative binomial regression models which found altitude, year, trap type, and island as categorized by human inhabitation to be significant factors influencing the distributions of both Ae. taeniorhynchus and Cx. quinquefasciatus. Annual differences at the highest altitudes in Isabela and Santa Cruz indicate the lack of a stable highland refuge if either species is found to be a major vector of a parasite, such as avian malaria in Galapagos. Further work is needed to confirm the vector potential of both species to understand the disease dynamics of avian malaria in Galapagos.     

Human activity can influence the gut microbiota of Darwin's finches in the Galapagos Islands

The gut microbiota of animal hosts can be influenced by environmental factors, such as unnatural food items that are introduced by humans. Over the past 30 years, human presence has grown exponentially in the Galapagos Islands, which are home to endemic Darwin's finches. Consequently, humans have changed the environment and diet of Darwin's finches, which in turn, could affect their gut microbiota. In this study, we compared the gut microbiota of two species of Darwin's finches, small ground finches (Geospiza fuliginosa) and medium ground finches (Geospiza fortis), across sites with and without human presence, where finches prefer human‐processed and natural food, respectively. We predicted that: (a) finch microbiota would differ between sites with and without humans due to differences in diet, and (b) gut microbiota of each finch species would be most similar where finches have the highest niche overlap (areas with humans) compared to the lowest niche overlap (areas without humans). We found that gut bacterial community structure differed across sites and host species. Gut bacterial diversity was most distinct between the two species at the site with human presence compared to the site without human presence, which contradicted our predictions. Within host species, medium ground finches had lower bacterial diversity at the site with human presence compared to the site without human presence and bacterial diversity of small ground finches did not differ between sites. Our results show that the gut microbiota of Darwin's finches is affected differently across sites with varying human presence.     

Effect of temperature on protein synthesis in fish of the Galapagos and Perlas Islands.

1. The temperature dependency of protein synthesis was studied in vivo in five species of Pacific fish collected in the Galapagos and Perlas Islands: batfish (Ogcocephalus darwini), groupers (Epinephelus labriformis), catfish (Netuma platypogan), puffers (Arothron hispidus) and triggerfish (Sufflamen verres). 2. Liver protein synthesis, assayed by a rapid pulse injection technique, showed a moderate temperature dependency (Q10 = 2-3) in the 15-30 degree C range for all species except puffers (Q10 = 10-20). Synthesis was inhibited above 32 degrees C. 3. Protein synthesis in triggerfish was measured by the constant-infusion technique. Synthetic rates (% of tissue protein synthesized per day) at 25 degrees C were 20% for liver, 10% for gill, 1.8% for red muscle and 0.6% for white muscle. Q10 in the 20 degrees-30 degrees C range was 3.0 +/- 0.5 degrees C for all tissues.     

Denitrification in Bahia Darwin (Galapagos Islands) an intermittent anoxic basin in the tropics

Changes in oxygen and nitrate in Bahia Darwin between July 1968 and March 1969 indicate that denitrification occurred in the deeper waters of this tropical, intermittently anoxic basin. Assuming constant rates of oxidation of organic matter in equally spaced depth intervals below the pycnocline depth, the rate of denitrification was estimated to be about 62.0 µg-atom NO₃-N/liter/year. This rate is attributable to denitrification in the water column because a smaller rate was estimated for strata closer to the sediment water interface.Contribution No. 3193 from the Woods Hole Oceanographic Institution. Woods Hole, Massachusetts 02543. This study was supported in part by the National Science Foundation Grants GA 29303 and GB 6870. Reprints should be requested from the second author.     

Observations on the distribution, ecology, and behaviour of bats on the Galapagos Islands

The distribution of bats on five Galapagos islands was assessed using ultrasonic detectors that can identify the feeding calls of different bat species. Red bats ( Lasiurus brachyotis ) were present on Santa Cruz and San Cristobal. Hoary bats ( L. cinereus ) were present on Santa Cruz, San Cristobal, Isabela, Floreana and Santiago. Species identifications were confirmed by recordings of bat calls, observations of flying bats, and the capture of 21 red bats and three hoary bats. There was no evidence of other species of bats on the Galapagos. Body size measurements were similar to those of South American red ( L. borealis ) and hoary ( L. c. villosissimus ) bats. Species status of L. brachyotis is not supported by morphological data. Both species were active in lowland and highland habitats, and foraging activity was high around street lights. Radio telemetry was used to locate day roosts and the nightly activity areas of four red bats in lowland areas of Santa Cruz. During the day, these bats roosted singly in the foliage of nine species of plant. Nightly activity areas were 10 to 20 ha in size. The activity areas of individuals overlapped, and included their known day roost sites. Both bat species were apparently more active in lowland habitats during the cool garua season, and less active in lowland habitats during the hot season. Female red bats were more abundant in lowland habitats during the cool season than were male red bats. Mesic, upland habitat may be critical to the survival of bats in the Galapagos.