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Chapter 3
Vertebrate Zoogeography
Introduction
Zoogeography is the study of the geographic distribution of animals and how they
(animals and environment) mutually influence each other
This will require a good knowledge of historical changes in climate, geography,
geomorphology, and species distribution
Faunal Zoogeography relates faunal lists to specific areas
It is the basis of all zoogeographic research
Comparative Zoogeography uses specific features and classify distributions
When comparing faunal assemblages from different areas, distributions may not
be consistent with present geological and geographical ranges
With some exception, most of the animals are not cosmopolitan in distribution.
The wide majority are limited to a particular region
When the limiting factors are many and specific, we are talking about a Narrowly
endemic species (or group of species)
Giant panda (Ailuropoda melanoleuca) bamboo forests in China
Tuataras (Sphenodon spp) islands on the coast of New Zealand
The distribution of a vertebrate species can be expressed as
1- its current Geographic range
2- its Geologic range
3- its Ecological distribution
1- Geographic range: land and/or water area where the sp currently occur
Disjunct distribution: Camelidae (Asia –camels and South America – llamas and
other spp)
2- Geologic range: taxon’s past and present distribution in time
3- Ecological distribution: its distribution in relation with the communities where
that sp belongs
Closely related spp – adjacent ranges
Center of distribution and center of speciation: areas from which the current
related spp evolve from their common ancestral form
What factors will affect the sp distribution?
1- means of dispersal
2- barriers to such dispersal
Barriers are relative
Three types:
1- Physical barriers
2- Climatic barriers
3- Biological barriers
1- Physical barriers: land, water, elevation soil type, topography, special cases
(roads for some small mammals)
2- Climatic barriers: temperature, humidity, rainfall, sunlight
3- Biological barriers: lack of food, presence of predator or competitor
Land bridges between North America and Eurasia, North America and South
America, Mozambique and Madagascar
A particularly well documented case, the migration of marsupials from South
America to Antarctica to Australia, where they went through an extensive
adaptive radiation without competition from placental mammals
Historical Zoogeography: attempt to provide explanations of spatial and temporal
distributions based on past events
Ecological Zoogeography: deals with present events and how those events
condition relationships at the community level
Distribution in time depends on continuing its reproductive potential
Distribution in space deals with the potential of a sp to move and occupy suitable
areas, always considering factors such as geography, geology, climate, ecology,
and human activity
Geographic Distribution: A.R. Wallace recognized that most taxa have congruent
distributions
He divided (based on affinities between terrestrial fauna and flora) the land
masses into six biogeographic regions, characterizing each region with a specific
faunal assemblage
Holarctic Region (Palearctic + Nearctic)
Oriental Region
Neotropical
Ethiopian Region
Australian Region
Holarctic Region (Palearctic + Nearctic)
Northern hemisphere (old and new world)
Palearctic Region: Europe & Asia
Nearctic Region: North America to central Mexico
Both regions imply circumpolar distribution, as with the Snowy owls (Nyctea
scandiaca), Arctic foxes (Alopex lagopus), and Polar bears (Ursus maritimus),
among others
Oriental Region: Asia south of the Himalayas (India, southeast Asia, Indonesia,
Philippines). Unique spp are Indiand & reticulated pythons (Python molurus and
P. reticulatus), king cobras (Ophiophagus hannah), gibbons (Hylobates spp),
orangutans (Pongo pygmaeus), Indian elephant (Elephas maximus), among
others
Neotropical Region: includes central and South America, including the Caribbean
islands, a stepping stone-corridor between the neotropical and the nearctic
regions. South American lung fish (Lepidosirenidae), poison-dart frogs
(Dendrobates & Phyllobates), anacondas (Eunectes murinus), rheas (Rhea sp),
toucans (Ramphastidae), South American Camelidae, anteater (Myrmecophaga
sp, Tamandua sp & Cyclopes sp), capybaras (Hydrochaeris hydrochaeris), etc.
Ethiopian Region: most of Africa, south of the Sahara desert, with endemics such
as Ostriches (Struthio camelus), zebras (Equus spp), gorillas (Gorilla gorilla),
aardvarks (Orycteropus afer), hippopotamuses (Hippopotamus amphibius), and
the African lung fish (Protopterus sp)
Australian Region: including Autralia, New Zealand, New Guinea, Tasmania and
other islands. The Wallace line separate this region from the Oriental. In
addition to the most diversely radiated marsupial assemblage, emus (Dromiceius
sp) cassowaries (Casuarius sp), platypus (Ornithorhynchus anatinus), echidnas
(Tachyglossus sp and Zaglossus sp) inhabit the region. Only two fully freshwater
fish species, Australian lung fish (Neoceratodus forsteri) and the barramundi
(Scleropages leichardti)
Geological Distribution
Earth was formed 4.6 billion years ago and life started as such at least 3.8 billion
years ago. Since then, Earth undergoes geological changes on its crust and
inside. The earth crust consist of rigid plates (about 100 km thick) floating on top
of a liquid-like mantle. These plates move around (very slowly) and re-arrange
its position along faults. Plate tectonics is how we call these movements. The
movements of these plates (and the continents) has significantly affected
climates, sea levels and therefore the distribution of vertebrates over time
600-400 million years ago (Cambrian to Silurian periods) six continents existed.
The plates moved and the continental masses collided to form super continents
that then split apart to form new ocean in between
Laurasia (Laurentia + Baltica) was formed between 420-360 mya, and later (360270 mya) collided with Gondwana to form the “world continent” Pangea
Pangea was not static and drifted northward causing dramatic climatic changes
Between 280-200 mya, higher latitudes were warm and moist, while low and
middle latitudes were much drier (regional differences in rainfall). At this time the
Appalachian Mountains were formed
By the late Triassic (210 mya) Pangea split into separate continents, forcing the
independent development of regional biotas (flora + fauna)
Asia and Africa began separating from each other (early Jurassic - 200 mya).
North America began to drift westward (continues today) and away from Africa
and South America (although still connected with Europe in the north)
By 100 mya (Jurassic-Cretaceous periods) sea level rises, flooding low-lying
areas creating shallow inland seas across North America, Eurasia and Canada.
At this time, the Sierra Nevada, Andes, Himalayas and Rocky Mountains were
formed, isolating regions and altering climate in vast areas
By the mid to late Cretaceous (80-60 mya) a massive regression of
epicontinental seas exposed land and altered climate and therefore biota
composition
The Atlantic Ocean is expanding since the early Tertiary (70 mys) to current
times due to a continuous westward drift of the Americas and sea levels
fluctuations. During the Pliocene (2-5 mya) Central America arose connecting
North and South America (which were isolated for many million years). This
event produced a phenomenon known as “the great american biotic interchange”
Earth has undergone a series of climatic shifts through time, with periods of rain
followed by droughts, cooler temps. alternated with warmer periods
Changes in temps caused changes in sea levels, which in terms caused the
formation of filters for dispersals
Glaciations have occurred several times, with the Wisconsin glaciation as the
most recent one. These events not only change the sea level but also altered
the biotic composition on extensive areas, restricting distributions toward the
tropics and in some cases, when glacials receded, producing disjunct
distributions and disjunct species
Ecological Distribution
Based on major environmental factors such as water, salinity, humidity,
temperature, light, oxygen, pressure and food, vertebrate distribute around the
globe
There are three (3) major ecological environments recognized: marine, fresh
water and terrestrial
Marine
the largest (70% Earth’s surface)
a vast, interconnected mass
variables?
temps (-2.2 to 32 ºC, w/local ranger never larger than 5 ºC)
depths (0 to 10.8 km)
salinity (35 ppt)
sunlight
Photic vs. Aphotic (w/1,000 mts as the recognized limit)
also pressure (increase rate of 1 atmosphere -14.7 lbs/inch²- for every 10 mts
depth)
Pelagic -open waters- (neritic + oceanic) & Benthic -ocean floor- regions
Neritic zone: cetaceans (whales, dolphins), reptiles (sea turtles, sea snakes),
fish, other mammals (sea otter)
Abyssopelagic zone (3-6 km): Rattails (Macrouridae), brotulas (Ophidiidae),
batfishes (Ogcocephalidae); most eel-like, blind, well developed cephalic lateralline canals and senses of smell and touch
Hadopelagic zone (more than 6 km): deepest living fish known – Abyssobrotula
galatheae, lives between 3-8.3 km deep
Fresh Water
the smallest, from rain puddles to lakes and rivers
Lotic (moving) and lentic (still) systems
variables?
temps (freezing to boiling)
clear or turbid
oxygen
salinity (0-0.5 ppt)
depths (0 to 1.7 km or more ?)
pH (CO2, organic acids or pollution)
Lotic environments will present a gradient of variables, from a very rapid flowing
bodies, where species such as salmonids present strong lateral muscles, to
slow-flowing streams, where bass and sunfishes (Centrarchidae), perches and
darters (Percidae), shiners or minnows (Cyprinidae), pikes (Esocidae), and
suckers (Catostomidae)
Lentic bodies (lakes, ponds, etc) contain four life zones
Littoral: closer to shore, rooted vegetation
Limnetic: main body of water
Both zones inhabited or used by all classes of vertebrates
In deep lakes, Profundal zone: open water below depth of light penetration (fish
adapted to cooler, darker waters & Benthic zone: bottom of the lake
(decomposers)
Catadromous: most of their adult lives in freshwaters and return to the sea to
reproduce (eels)
Anadromous: most of their adult lives in the ocean and return to the rivers to
reproduce (salmons)
Terrestrial
the most variable of all 3 environments
variables?
elevation (bellow sea level to 8.5 km)
air temps (-60 to 60 ºC, increasing at a rate of 1.2 ºC for every 305 mts in
elevation)
pption (from a fraction of a cm to 1.3 mts/year
Based on these variables, there are different ways to classify terrestrial
environments: biomes, life zones, and biotic provinces
Biomes: based on natural climaxic communities (Clements & Shelford, 1939)
Tundra: around the Arctic circle (up to 2,000 km south), 20 cm of pption,
seasonal photoperiodic fluctuation, permafrost, flowering and fruiting cycles very
quick
Permanent residents: lemmings (Lemmus spp, Dicrostonyx spp), ptarmigan
(Lagopus sp), musk-ox (Ovibos moschatus), polar bears (Ursus maritimus),
caribou (Rangifer tarandus)
Taiga: coniferous forests north of Eurasia and North America (and high
elevetions southward), cold winters and short summers, pption .4-1 mt/y (much
as snow), growing season of about 130 days, little light reaches the ground
Permanent residents: Snowy owls (Nyctea scandiaca), crossbills (Loxia sp), lynx
(Lynx canadensis), wolves (Canis lupus), moose (Alces alces), and bears (Ursus
spp)
Temperate Deciduous forests: south of the Taiga (in most cases), dominated by
deciduous forests species, four well-defined seasons, a growing season of up to
300 days, pption .75 to 1.5 mts, good amount of light reaches the ground
Permanent residents: certain salamanders (Plethodontidae), skinks (Eumeces
spp), garter snakes (Thamnophis spp), turkeys (Meleagris gallopavo), pileated
woodpecker (Hylatomus pileatus), squirrels (Sciurus spp), bobcats (Lynx rufus),
foxes (Vulpes spp & Urocyon spp), white-tailed deer (Odocoileus virginianus)
Grasslands: enough water for grass but not enough for trees (.2 mts), seasonal
droughts and fires, very rich and well-developed soils, called “prairies”
(temperate), “savannas” (tropical) or even “mediterranean chaparrals” (rain
during winter, resulting a mixture of grass and shrubby scrublands)
Permanent residents: for prairies - other skink spp (Eumeces spp), rattlesnakes
(Crotalus spp), burrowing owls (Speotyto cunicularia), prairie dogs (Cynomys
spp), coyotes (Canis latrans), bison (Bison bison); for savannas – elephants
(Loxodonta africana), giraffes (Giraffa camelopardalis), many other spp of large
and medium herbivores, lions (Panthera leo), cheetahs (Acinonyx jubatus), and
hyenas (Hyaena spp)
Deserts: larger in Africa, Asia and Australia and smaller in North and South
America, hot days and cool nights, less than .25 mt/y, vegetation very sparse,
many animal spp are burrowers, common adaptations include reduction of
cutaneous glands, concentrated urine, and dry feces, many metabolize water
from food and also estivate (inactivity during summer), many rodents from xeric
habitats all over the world developed similar suit of characters (morphological,
physiological, and ecological convergence)
Permanent residents: Gila monsters (heloderma suspectum), rattlesnakes
(Crotalus sp), roadruners (geococcyx californicus), and kangaroo rats
(Dipodomys spp)
Tropical Forests: two major types – tropical deciduous forests & tropical rain
forests, more than 2.5 mts/y in pption combined with continual warmth (20-25
ºC), makes these the richest biome. With multilayer canopy, epiphytes, lianas,
and woody vines and a dense understory. Morphological convergence is
strikingly evident between African and South American rain forest’s vertebrates
Permanent residents: treefrogs (Hylidae), tree (or green) iguanas (Iguanidae),
caimans (Caiman crocodilus), parrots (Psitacidae), monkeys (Saimiri spp, Cebus
spp, Alouatta spp, among others), and jaguars (Panthera onca)
Life Zones: proposed by C. Hart Merriam, based on 1- animals and plants are
restricted in northward distribution by the total heat during the growing and
reproductive season and 2- animals and plants are restricted in southward
distribution by the mean temp of the hottest part of the year
Each zone has a temp range of about 4ºC. Three regions (Boreal, Austral and
Tropical) with life zones within
Boreal region: it includes the Arctic-Alpine, Hudsonian, and canadian zones with
examples of permanent residents for the Arctic-Alpine zone: arctic foxes (Alopex
lagopus), Arctic hares (Lepus arcticus), and lemmings (Lemmus spp and
Dicrostonyx spp); for the Hudsonian zone: great gray owls (Strix nebulosa),
moose (Alces alces), and wolverine (Gulo gulo); and for the canadian zone:
spruce grouse (Canachites canadensis), varying hares (Lepus americanus), and
lynx (Lynx canadensis)
Austral region: with also three zones Transitional, Upper and lower zones.
Transition zone, with population residents: sage and sharp-tailes grouses
(Centrocercus sp & Pedioecetes sp), northern flying squirrels (Glaucomys
sabrinus), and black bears (Ursus americanus)
Upper (sonoran) austral zone: eastern wood frogs (Rana sylvatica), cardinals
(Richmondena cardinalis), eastern wood rats (Neotoma spp) & ring-tailed cats
(Bassariscus astutus), and northern grasshoper mice (Onychomys spp)
Lower (sonoran) austral region: frogs (Rana spp), alligator snapping turtles
(Macroclemys temminki), anoles (Anolis spp), brown pelicans (Pelicanus
occidentalis), rats (Oryzomys spp, Sigmodon spp) & kit foxes (Vulpes macrotis),
kangaroo rats (Dipodomys spp) and pocket mices (Perognathus spp)
Tropical region divided into arid and humid life zones (an oversimplification of a
much more complex system)
Biotic Provinces, a third method of classification of North American plants and
animals is characterized by important ecological associations (climaxic
ecosystems, fauna, climate, physiology and soils) and is based on vegetation
types
Biotic provinces are subdivided into biotic districts and “vertical” life belts.
Boundaries are physiographical barriers and varies from time to time (ecological
successions, climate changes)
Changes (in distribution) caused by human activity
-
Domestication, dogs, cats, cattle, goats, horses, pigs
-
Extinction, introduced predators reduced geographic ranges (to local or
complete extinction)
-
Habitat alteration, construction of reservoirs, artificial canals, cutting
forests, produces disturbances in nature, helping certain spp to thrive -Coyote (Canis latrans), white-tailed deer (Odocoileus virginianus) and
others to disappear --Cougars (Felis concolor) and wolves (Canis lupus
and C. rufus)
-
Transport / introductions, european rabbits (Oryctolagus cuniculus),
Norway rat (Rattus norvegicus), house mouse (Mus musculus), starlings
(Sturnus vulgaris), English house sparrows (Passer domesticus),
Mongooses (Herpestes spp), nutria (Myocastor coypu), special note on
the accidental releases of hundreds of exotic spp (pet trade) in Florida or
successful introductions of spp that benefited environment and economy
(ringnecked pheasants (Phasianus colchicus) and eastern gray partridge
(Perdix perdix)