scholarly journals Origin of elevational replacements in a clade of nearly flightless birds – most diversity in tropical mountains accumulates via secondary contact following allopatric speciation

2019 ◽  
Author(s):  
Carlos Daniel Cadena ◽  
Laura N. Céspedes
Keyword(s):  
Species Turnover ◽  
Secondary Contact ◽  
Elevational Gradients ◽  
Closely Related Species ◽  
Tropical Mountains ◽  
Limited Dispersal ◽  
Phylogenetic Framework ◽  
Parapatric Speciation ◽  
The Tropics

AbstractTropical mountains are biodiversity hotspots. In particular, mountains in the Neotropics exhibit remarkable beta diversity reflecting species turnover along elevational gradients. Elevational replacements of species have been known since early surveys of the tropics, but data on how such replacements arise are scarce, limiting our understanding of mechanisms underlying patterns of diversity. We employed a phylogenetic framework to evaluate hypotheses accounting for the origin of elevational replacements in the genusScytalopus(Rhinocryptidae), a speciose clade of passerine birds with limited dispersal abilities occurring broadly in the Neotropical montane region. We found that species ofScytalopushave relatively narrow elevational ranges, closely related species resemble each other in elevational distributions, and most species replacing each other along elevational gradients are distantly related to each other. Although we cannot reject the hypothesis that a few elevational replacements may reflect parapatric speciation along mountain slopes, we conclude that speciation inScytalopusoccurs predominantly in allopatry within elevational zones, with most elevational replacements resulting from secondary contact of formerly allopatric lineages. Our study suggests that accumulation of species diversity in montane environments reflects colonization processes as opposed toin situdivergence even in dispersal-limited animals.

Evolutionary conservatism will limit responses to climate change in the tropics

2021 ◽  
Vol 17 (10) ◽  
Author(s):  
Ethan B. Linck ◽  
Benjamin G. Freeman ◽  
C. Daniel Cadena ◽  
Cameron K. Ghalambor
Keyword(s):  
Thermal Tolerance ◽  
Species Turnover ◽  
Tropical Species ◽  
Evolutionary Divergence ◽  
Closely Related Species ◽  
Tropical Mountains ◽  
Low Latitudes ◽  
Parapatric Speciation ◽  
The Tropics

Rapid species turnover in tropical mountains has fascinated biologists for centuries. A popular explanation for this heightened beta diversity is that climatic stability at low latitudes promotes the evolution of narrow thermal tolerance ranges, leading to local adaptation, evolutionary divergence and parapatric speciation along elevational gradients. However, an emerging consensus from research spanning phylogenetics, biogeography and behavioural ecology is that this process rarely, if ever, occurs. Instead, closely related species typically occupy a similar elevational niche, while species with divergent elevational niches tend to be more distantly related. These results suggest populations have responded to past environmental change not by adapting and diverging in place, but instead by shifting their distributions to tightly track climate over time. We argue that tropical species are likely to respond similarly to ongoing and future climate warming, an inference supported by evidence from recent range shifts. In the absence of widespread in situ adaptation to new climate regimes by tropical taxa, conservation planning should prioritize protecting large swaths of habitat to facilitate movement.

scholarly journals Speciation and gene flow across an elevational gradient in New Guinea kingfishers

2019 ◽  
Author(s):  
Ethan Linck ◽  
Benjamin G. Freeman ◽  
John P. Dumbacher
Keyword(s):  
Gene Flow ◽  
Nuclear Dna ◽  
New Guinea ◽  
Ecological Speciation ◽  
High Elevation ◽  
Divergent Selection ◽  
Secondary Contact ◽  
Gene Trees ◽  
Tropical Mountains

AbstractClosely related species with parapatric elevational ranges are ubiquitous in tropical mountains worldwide. The gradient speciation hypothesis proposes that these series are the result of in situ ecological speciation driven by divergent selection across elevation. Direct tests of this scenario have been hampered by the difficulty inferring the geographic arrangement of populations at the time of divergence. In cichlids, sticklebacks, and Timema stick insects, support for ecological speciation driven by other selective pressures has come from demonstrating parallel speciation, where divergence proceeds independently across replicated environmental gradients. Here, we take advantage of the unique geography of the island of New Guinea to test for parallel gradient speciation in replicated populations of Syma kingfishers that show extremely subtle differentiation across elevation and between historically isolated mountain ranges. We find that currently described high elevation and low elevation species have reciprocally monophyletic gene trees and form nuclear DNA clusters, rejecting this hypothesis. However, demographic modeling suggests selection has likely maintained species boundaries in the face of gene flow following secondary contact. We compile evidence from the published literature to show that while in situ gradient speciation in labile organisms such as birds appears rare, divergent selection and post-speciation gene flow may be an underappreciated force in the origin of elevational series and tropical beta diversity along mountain slopes.

scholarly journals Staying cool: preadaptation to temperate climates required for colonising tropical alpine-like environments

PhytoKeys ◽  
2018 ◽  
Vol 96 ◽  
pp. 111-125 ◽  
Author(s):  
Berit Gehrke
Keyword(s):  
Environmental Gradients ◽  
Temperate Climate ◽  
Tropical Mountains ◽  
Mountainous Regions ◽  
Tropical Environments ◽  
Tropical Alpine ◽  
Suitable Habitats ◽  
The Tropics ◽  
The Impact

Plant species tend to retain their ancestral ecology, responding to temporal, geographic and climatic changes by tracking suitable habitats rather than adapting to novel conditions. Nevertheless, transitions into different environments or biomes still seem to be common. Especially intriguing are the tropical alpine-like areas found on only the highest mountainous regions surrounded by tropical environments. Tropical mountains are hotspots of biodiversity, often with striking degrees of endemism at higher elevations. On these mountains, steep environmental gradients and high habitat heterogeneity within small spaces coincide with astounding species diversity of great conservation value. The analysis presented here shows that the importance ofin situspeciation in tropical alpine-like areas has been underestimated. Additionally and contrary to widely held opinion, the impact of dispersal from other regions with alpine-like environments is relatively minor compared to that of immigration from other biomes with a temperate (but not alpine-like) climate. This suggests that establishment in tropical alpine-like regions is favoured by preadaptation to a temperate, especially aseasonal, freezing regime such as the cool temperate climate regions in the Tropics. Furthermore, emigration out of an alpine-like environment is generally rare, suggesting that alpine-like environments – at least tropical ones – are species sinks.

Community characteristics of forest understory birds along an elevational gradient in the Horn of Africa: A multi-year baseline

The Condor ◽  
2021 ◽  
Author(s):  
Kyle D Kittelberger ◽  
Montague H C Neate-Clegg ◽  
Evan R Buechley ◽  
Çağan Hakkı Şekercioğlu
Keyword(s):  
Species Richness ◽  
Species Turnover ◽  
Survival Rates ◽  
Elevational Gradient ◽  
Forest Understory ◽  
Bird Abundance ◽  
Tropical Mountains ◽  
Demographic Rates ◽  
Understory Birds ◽  
Over Time

Abstract Tropical mountains are global hotspots for birdlife. However, there is a dearth of baseline avifaunal data along elevational gradients, particularly in Africa, limiting our ability to observe and assess changes over time in tropical montane avian communities. In this study, we undertook a multi-year assessment of understory birds along a 1,750 m elevational gradient (1,430–3,186 m) in an Afrotropical moist evergreen montane forest within Ethiopia’s Bale Mountains. Analyzing 6 years of systematic bird-banding data from 5 sites, we describe the patterns of species richness, abundance, community composition, and demographic rates over space and time. We found bimodal patterns in observed and estimated species richness across the elevational gradient (peaking at 1,430 and 2,388 m), although no sites reached asymptotic species richness throughout the study. Species turnover was high across the gradient, though forested sites at mid-elevations resembled each other in species composition. We found significant variation across sites in bird abundance in some of the dietary and habitat guilds. However, we did not find any significant trends in species richness or guild abundances over time. For the majority of analyzed species, capture rates did not change over time and there were no changes in species’ mean elevations. Population growth rates, recruitment rates, and apparent survival rates averaged 1.02, 0.52, and 0.51 respectively, and there were no elevational patterns in demographic rates. This study establishes a multi-year baseline for Afrotropical birds along an elevational gradient in an under-studied international biodiversity hotspot. These data will be critical in assessing the long-term responses of tropical montane birdlife to climate change and habitat degradation.

Species turnover on elevational gradients in small rodents

2005 ◽  
Vol 14 (6) ◽  
pp. 539-547 ◽  
Author(s):  
José Luis Mena ◽  
Ella Vázquez-Domínguez
Keyword(s):  
Species Turnover ◽  
Small Rodents ◽  
Elevational Gradients

scholarly journals Karyotype Characterization of Nine Periwinkle Species (Gastropoda, Littorinidae)

Genes ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 517 ◽  
Author(s):  
Daniel García-Souto ◽  
Sandra Alonso-Rubido ◽  
Diana Costa ◽  
José Eirín-López ◽  
Emilio Rolán-Álvarez ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Chromosome Numbers ◽  
Gene Clusters ◽  
Chromosomal Mapping ◽  
Closely Related Species ◽  
Submetacentric Chromosome ◽  
The Family ◽  
Littorina Arcana

Periwinkles of the family Littorinidae (Children, 1834) are common members of seashore littoral communities worldwide. Although the family is composed of more than 200 species belonging to 18 genera, chromosome numbers have been described in only eleven of them. A molecular cytogenetic analysis of nine periwinkle species, the rough periwinkles Littorina arcana, L. saxatilis, and L. compressa, the flat periwinkles L. obtusata and L. fabalis, the common periwinkle L. littorea, the mangrove periwinkle Littoraria angulifera, the beaded periwinkle Cenchritis muricatus, and the small periwinkle Melarhaphe neritoides was performed. All species showed diploid chromosome numbers of 2n = 34, and karyotypes were mostly composed of metacentric and submetacentric chromosome pairs. None of the periwinkle species showed chromosomal differences between male and female specimens. The chromosomal mapping of major and minor rDNA and H3 histone gene clusters by fluorescent in situ hybridization demonstrated that the patterns of distribution of these DNA sequences were conserved among closely related species and differed among less related ones. All signals occupied separated loci on different chromosome pairs without any evidence of co-localization in any of the species.

Colonization of depopulated crinoids by symbionts: who comes from the bottom and who from the water column?

2015 ◽  
Vol 95 (8) ◽  
pp. 1607-1612 ◽  
Author(s):  
E.S. Mekhova ◽  
P.Y. Dgebuadze ◽  
V.N. Mikheev ◽  
T.A. Britayev
Keyword(s):  
Water Column ◽  
Field Experiments ◽  
Dispersal Ability ◽  
Long Distance ◽  
Sandy Substrate ◽  
Limited Dispersal ◽  
Set Up ◽  
Almost All ◽  
High Degree

Previous experiments with the comatulid Himerometra robustipinna (Carpenter, 1881) demonstrated intensive host-to-host migration processes for almost all symbiotic species both within host aggregations and among hosts separated by several metres. The aim of this study was to check the ability of symbionts to complete long-distance migrations, by means of two in situ experiments which depopulated the crinoid host. Two different sets of field experiments were set up: exposure of depopulated crinoids (set 1) on stony ‘islands’ isolated from native crinoid assemblages by sandy substrate, and (set 2) in cages suspended in the water column. Hosts from set 1 were exposed for 1, 2, 3 and 4 weeks to assess whether substrate has an influence on the symbionts' long-distance migrations. In set 2 cages were exposed for 10–11 days, aiming to check whether symbionts were able to disperse through the water column with currents. These experiments allow the conclusion that post-settled symbionts can actively migrate among their hosts. Symbionts are able to reach their hosts by employing two different ‘transport corridors’, by drifting or swimming in water column, and by moving on the bottom. Comparison of experimental results allows the division of symbionts into two conventional groups according to the dispersal ability of their post-settled stages: (1) species able to complete long-distance migrations, (2) species unable to migrate or having limited dispersal ability. The finding of the free-living shrimp Periclimenes diversipes Kemp, 1922 in set 2 raises the question about the factors that affect such a high degree of specialization of crinoid assemblages.

The Joint ESA-NASA Tropical Campaign Activity – Aeolus Calibration/Validation and Science in the Topics

2021 ◽  
Author(s):  
Thorsten Fehr ◽  
Gail Skofronick-Jackson ◽  
Vassilis Amiridis ◽  
Jonas von Bismarck ◽  
Shuyi Chen ◽  
...  
Keyword(s):  
Weather Prediction ◽  
Cape Verde ◽  
World Population ◽  
Aerosol Layer ◽  
Mean Flow ◽  
Western Atlantic ◽  
Convective Systems ◽  
Wide Range ◽  
The Tropics

<p>The Tropics are covering around 40% of the globe and are home to approximately 40% of the world population. However, numerical weather prediction (NWP) for this region still remains challenging due to the lack of basic observations and incomplete understanding of atmospheric processes, also affecting extratropical storm developments. As a result, the largest impact of the ESA’s Aeolus satellite observations on NWP is expected in the Tropics where only a very limited number of wind profile observations from the ground can be performed.</p><p>An especially important case relating to the predictability of tropical weather system is the outflow of Saharan dust, its interaction with cloud micro-physics and the overall impact on the development of tropical storms over the Atlantic Ocean. The region of the coast of West Africa uniquely allows the study of the Saharan Aerosol layer, African Easterly Waves and Jets, Tropical Easterly Jet, as well as the deep convection in ITCZ and their relation to the formation of convective systems and the transport of dust.</p><p>Together with international partners, ESA and NASA are currently implementing a joint Tropical campaign from July to August 2021 with its base in Cape Verde. The campaign objective is to provide information on the validation and preparation of the ESA missions Aeolus and EarthCARE, respectively, as well as supporting a range of related science objectives for the investigation in the interactions between African Easterly and other tropical waves with the mean flow, dust and their impact on the development of convective systems; the structure and variability of the marine boundary layer in relation to initiation and lifecycle of the convective cloud systems within and across the ITCZ; and impact of wind, aerosol, clouds, and precipitation effects on long range dust transport and air quality over the western Atlantic.</p><p>The campaign comprises a unique combination of both strong airborne and ground-based elements collocated on Cape Verde. The airborne component with wind and aerosol lidars, cloud radars, in-situ instrumentation and additional observations includes the NASA DC-8 with science activities coordinated by the U. of Washington, the German DLR Falcon-20, the French Safire Falcon-20 with activities led by LATMOS, and the Slovenian Aerovizija Advantic WT-10 light aircraft in cooperation with the U. Novo Gorica. The ground-based component led by the National Observatory of Athens is a collaboration of more than 25 European teams providing in-situ and remote sensing aerosol and cloud measurements with a wide range of lidar, radar and radiometer systems, as well as drone observatins by the Cyprus Institute.</p><p>In preparation for the field campaign, the NASA and ESA management and science teams are closely collaborating with regular coordination meetings, in particular in coordinating the shift of the activity by one year due to the COVID-19 pandemic. The time gained has been used to further consolidate the planning, and in particular with a dry-run campaign organized by NASA with European participation where six virtual flights were conducted in July 2020.</p><p> This paper will present a summary of the campaign preparation activities and the consolidated plan for the 2021 Tropical campaign.</p>

Subvisual Cirrus

Cirrus ◽  
2002 ◽  
Author(s):  
David K. Lynch ◽  
Kenneth Sassen
Keyword(s):  
World War Ii ◽  
Solar Limb ◽  
Stratospheric Aerosol ◽  
Defense Meteorological Satellite Program ◽  
Passive Sensors ◽  
The Tropics ◽  
Anvil Cirrus ◽  
High Clouds ◽  
Meteorological Satellite

Starting during World War II, pilots flying high over the tropics reported “a thin layer of cirrus 500ft above us”. Yet as they ascended, they still observed more thin cirrus above them, leading to the colloquialism “cirrus evadus.” With the coming of lidar in the early 1960s, rumors and unqualified reports of subvisual cirrus were replaced with validated detections, in situ sampling, and the first systematic studies (Uthe 1977; Barnes 1980, 1982). Heymsfield (1986) described observations over Kwajalein Atoll in the western tropical Pacific Ocean, where pilots and lidars could clearly see the cloud but DMSP (U.S. Defense Meteorological Satellite Program) radiance measurements and ground observers could not. The term “subvisual” is a relatively recent appellation. Prior terminology included cirrus haze, semitransparent cirrus, subvisible cirrus veils, low density clouds, fields of ice aerosols, cirrus, anvil cirrus, and high altitude tropical (HAT) cirrus. Subvisual cirrus clouds (SVC) are widespread (Winker and Trepte 1998; see chapter 12, this volume) and virtually undetectable with existing passive sensors. Orbiting solar limb occupation systems such as the Stratospheric Aerosol and Gas Experiment (SAGE) can detect these clouds, but only by looking at them horizontally where the optical depths are significant. SVC appear to affect climate primarily by heating the planet, though to what extent this may happen is unknown. Much of what we know is based on work by Heymsfield (1986), Platt et al. (1987), Sassen et al. (1989, 1992), Flatau et al. (1990), Liou et al. (1990), Hutchinson et al. (1991, 1993), Dalcher (1992), Sassen and Cho (1992), Takano et al. (1992), Lynch (1993), Schmidt et al. (1993), Schmidt and Lynch (1995), and Winker and Trepte (1998). SVC are defined as any high clouds composed primarily of ice (WMO 1975) and whose vertical visible optical depth is 0.03 or less (Sassen and Cho 1992). Such clouds are usually found near the tropopause and are less than about 1 km thick vertically. SVC do not appear to be fundamentally different from ordinary, optically thicker cirrus. They do, however, differ from average cirrus by being colder (-50-90°C), thinner (<0.03 optical depths at 0.694 μm), and having smaller particles (typically about <50μm diameter).

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