Presentation on theme: "Evolution in NZ Geological Time Scale Some useful information. Significant Geological Events Biological Factors that have shaped NZ’s Flora and."— Presentation transcript:
Evolution in NZ Geological Time Scale Some useful information. Significant Geological Events Biological Factors that have shaped NZ’s Flora and Fauna.
ErasEpochsPeriods Age (millions of years) CenozoicQuaternaryRecentPleistocene0.011.8 TertiaryPliocene5 Miocene23 Oligocene35 Eocene57 Paleocene65 Known as K/T boundary MesozoicCretaceous144 Jurassic206
The Key Factors that have shaped NZ’s Biota are: Isolation – NZ has been isolated from other land masses for 65 million years. Lack of terrestrial mammals – many of the niches occupied by mammals in other parts of the world have been filled by a diversity of birds, insects and reptiles. Lack of mammalian predators has allowed species to develop in a way that has ill suited them to the influx of humans and their mammal associates. Size – NZ has a relatively small landmass that at times has been considerably smaller.
There are two basic processes which explain why a species occurs in a specific area : Dispersal – a species can move itself to eg NZ on currents, winds, by floating, flying, on rafts of vegetation. Vicariance -The earth itself can move the species by continental drift. Species that were present in Gondwanaland when NZ drifted away from Australia 80 ma are vicariant groups.
New Zealand’s flora and fauna (biota) are a mixture of vicariant and dispersed types.
Organisms present during the Cretaceous (vicariant groups) Dinosaurs Ratites Wrens Tuatara Frogs (Leiopelma) Like being on Noah’s Ark! They will drift with NZ. They are the “Gumboot Gang” Peripatus Giant Land Snails Skinks Geckos Beeches Kauris Podocarps
Significant Events in NZ’s Geological History These specific occurrences have made NZ the unique place it is.
Gondwana breaks up. During the Jurassic Period, Gondwana begins to break apart. NZ is connected to Australia and Antarctic portions (fully for the first time) and terrestrial plants and animals from Gondwana colonise NZ.
The K/T boundary Mass Extinctions K/T boundary (Cretaceous/Tertiary) was 65 ma. An estimated 85% of all living species at the time are wiped out by a mass extinction event – probably a massive asteroid strike. This was the end of the Age of Dinosaurs and the rise of the mammals (adaptive radiation into all the empty niches)
Losing Australia in the Paleocene! 60 ma the Tasman Sea is fully open and NZ has geographical isolation from Australia. However there are probably not many mammals aboard when NZ starts its journey away from Australia*. Founder Effect. *See list of organisms on slide 6
Drowning in the Oligocene 35 ma, NZ was reduced to islands separated by waterways. 18% of today’s land mass remained. Habitat was severely depleted, the temperature was lowered. Reduction in genetic diversity had a large effect on NZ fauna The bottleneck effect
Making Mountains in the Miocene Miocene is 23 – 5 ma In the mid-Miocene, the Kaikoura Orogeny(mountain building) thrust up the Southern Alps, and NZ’s other mountains. Geographic Isolation
Freezing in the Pleistocene. Ice Ages occurred from 1.8 ma to 14,000 years BP. Cyclical cooling with glaciers advancing; sea levels dropping and land bridges being created with offshore islands. Every 5000 years the interglacial phase caused warmer conditions; glaciers retreating; sea levels rising.
What now? We are in an interglacial at present. We also seem to be in the middle of the sixth of the great mass extinctions that have occurred approximately every 100 million years since the Cambrian Period. It takes another 5 – 10 million years for species diversity to recover from these mass extinction events.
Biological Factors that have shaped NZ’s Flora and Fauna.
Flowers and Pollination We have no indigenous long-tongued bee species (social bees) Most flowers rely on unspecialised agents for pollination so have generalised flowers not adapted to one specific pollinator. Flowers tend to be small and unshowy (often white)
Pollinators are indigenous short-tongued bees; some butterflies; some beetles and moths; flies; birds and bats. Some plants have specialised: –Wood rose and short tailed bat –Mistletoe and tuis or bellbirds –Hebe – some specialised adaptations for insects. –Red flowers for bird pollinators.
Dioecious Plants Because of the lack of specialised pollinators, there may be a problem with self-fertilisation occurring more than is desirable. Dioecious plants have male and female reproductive structures on separate plants and so reduce this problem.
Animal Specialties. Flightlessness conserved energy in cold conditions and could flourish in the absence of terrestrial mammal predators. Gigantism is another adaptive feature favouring heat retention. Melanism also favours heat retention and energy conservation.
Melanism Some NZ birds are dimorphic with a naturally occurring melanic form within the species. The fantail is an example with the melanic form being more common in the South Island, bearing out the heat retention idea.
Flightlessness Most common on isolated islands free of mammalian predators. Significant in - Ratites – Moa and Kiwi -Rails – Takahe and Weka -Adzebill – now extinct. -Wrens – four of the extinct wrens were flightless. -Kakapo is the world’s only flightless parrot. -Weta, earwigs and stick insects also show flightlessness.
Reduced Reliance on Flight Many of our bird species are weak fliers – the wattle birds like Kokako – blue-wattled crow, Saddle back and Huia (now extinct) Lesser short-tailed bats (Mystacina tuberculata, spend most of their time foraging on the ground.
Gigantism Haast’s Eagle, Adzebill, Moa, flightless goose, Sea Eagle – all extinct. Takahe, Kakapo Giant invertebrates – wetas. Once again, this is a characteristic that was able to develop in the absence of mammalian predators.