Land Plant Evolution: Land Plant Evolution: Algae to Angiosperms Algae to Angiosperms The greatest adaptive radiation . • is the largest radiation of plants • involves series of dramatic adaptations to the problem of life on land and being non- motile • exhibits successive rounds of speciation and subsequent extinction • sets the stage for the development of a land-based ecosystem with fungi and animals Angiosperms - Flowering Plants Fungi? • Fungi collectively are not a natural group Angiosperms focus of the course • More closely related to animals than to plants • comprise the phylum Magnoliophyta • contains majority of plant diversity take Botany 332 – spring 2019 What are the non-angiosperm land plants? • DNA evidence has clarified much but not all of the relationships of other phyla See first pages of Chpts 1 & Chpts 3-4 for more detail (Plant Systematics, 2nd ed.) 1 Fungi? Charales - stoneworts • Green algal lineage take Botany 330 – fall 2019 Recent view of • Closest relatives to land plants eukaryotic relationships • root is in microbes with fungi/animals/plants forming a crown radiation Fungi are here Green Plants are here we are here Charales - stoneworts Extinct Land Plants - the first plants Ordovician Period (505 - 440 mya) take Botany 330 – fall 2019 • Green algal lineage • First evidence of land life at 460 mya • Closest relatives to land plants Microfossils of spores with sporopollenin (degradation resistant material like lignin) and similar to modern day bryophytes such as liverworts Starry stonewort Nitellopsis obtusa L. Found worldwide in shales that were deposited at the marine-terrestrial interface Wisconsin’s latest (and greatest?) lake invasive 2 bryophytes bryophytes • earliest land plants - non vascular • gametophyte dominant, 16000 species • 3 lineages — they are not a natural group hornworts mosses mosses Liverworts - Marchantiophyta Mosses - Bryophyta Hornworts - Anthoceratophyta liverworts liverworts Extinct Land Plants - first vascular plants Lycopodiophyta - club mosses Early Devonian Period (410 - 390 mya) • 3 families, 1150 species Rhynia seen in the early Devonian (Rhynie • sporophyte dominant, vascular, free sporing Chert fossil) is one of first vascular plants • they are sister to all other vascular plants 20 cm tall, no roots, no leaves, primitive vascular tissue Lycopodium - club mosses Isoetes - quillworts Selaginella - spike mosses 3 Extinct Land Plants - the first ferns Polypodiophyta - ferns Late Devonian Period (390 - 360 mya) • 11000 species (or called “Monilophyta”) • immense variation in habit and habitat • spores produced in specialized sporangia • need a lot of systematic work - tropics! First true ferns [Protopteridium] - free sporing with complex sporangia & megaphylls Polypodiophyta - ferns Polypodiophyta - ferns • includes the horsetails as unusual ferns! • includes the strange whisk ferns! • 15 species in Equisetum • 6 species in 2 genera • vascular plants, reduced leaves, terminal • vascular plants, leafless green stemmed, sporangia lateral sporangia Psilotum habit Psilotum branch Psilotum sporangia 4 Extinct Land Plants - the seed plants Extinct Land Plants – first gymnosperms Late Devonian Period (390 - 360 mya) Permian Period (286 - 245 mya) First “seeds” - “seed ferns” [Archaeosperma] Plants fern-like with dissected compound leaves, but produce naked seeds (embryo within • Big trees with net-veined protective coverings) leaves • Seed bearing (derived from female gametophyte) and pollen forming (from male gametophyte) Pinophyta - gymnosperms Pinophyta - gymnosperms • 870 species • 870 species • seed plants but seeds naked • seed plants but seeds naked • often divided into 4 phyla conifers • often divided into 4 phyla • is one closer to angiosperms? • is one closer to angiosperms? cycads pine spruce juniper male strobilus female strobili 5 Pinophyta - gymnosperms Pinophyta - gymnosperms • 870 species • 870 species • seed plants but seeds naked • seed plants but seeds naked • often divided into 4 phyla • often divided into 4 phyla • is one closer to angiosperms? • is one closer to angiosperms? gnetophytes mature seeds ginkgo Gnetum Ephedra male strobili Welwitschia mirabilis Extinct Land Plants – first flowering plants Magnoliophyta - angiosperms Cretaceous Period (146 - 65 mya) Near the Jurassic/Cretaceous border, the first Angiosperms are seen • 275,000 + species (400,000 ?) • seed plants with seeds encased in ovary Triassic • flowers a “key innovation” Archaefructus 6 Angiosperms - Flowering Plants Angiosperms - Flowering Plants • tremendous adaptive radiation on • tremendous adaptive radiation on land (and back into water) land (and back into water) • Eucalyptus regnans (Myrtaceae) over 100m tall and 19m dbh Eucalyptus regnans (Myrtaceae) -Tasmania Angiosperms - Flowering Plants Angiosperms - Flowering Plants • tremendous adaptive radiation on • tremendous adaptive radiation on land (and back into water) land (and back into water) • Wolffia microscopica • Wolffia microscopica (Araceae) less than 1mm long (Araceae) less than 1mm long 0.1 mm • Amorphophallus titanum (Araceae) over 2 m tall 7 Angiosperms - Flowering Plants Angiosperms - Flowering Plants • tremendous adaptive radiation on • tremendous adaptive radiation on land (and back into water) land (and back into water) • largest inflorescence • largest numbers of flowers — Amorphophallus titanum (Araceae) Corypha palm Angiosperms - Flowering Plants Angiosperms - Flowering Plants • tremendous adaptive radiation on land (and back into water) • largest flower: Rafflesia arnoldii Magnoliophyta classification (Rafflesiaceae) from New Guinea, up to 1m across and 20lbs • previously divided into two classes — dicots and monocots • artificial! • we will use Angiosperm Phylogeny Group (APG III) classification system of 2009 8 Angiosperms or Flowering Plants The Flower — Why Important? the Phylum Magnoliophyta The Flower: most significant feature of angiosperms 1. unlike anything else in other plants & extremely Today & Monday: overview of the morphology variable & co-evolved with animals and evolution of the flower – optionally read first 2. floral features used in describing and id’ing part of Chpt. 6 in Plant Systematics, 2nd ed. – 3. plant specimens (herbarium) must include flowers or available at Canvas/Learn@UW derived features 4. classification of angiosperms relies on flowers Lab next two weeks: (1) vegetative features st & conifers – 1 half of Chpt 9 in Plant Calochortus - fairy lanterns & mariposas (images: T. Givnish) Systematics; (2) finish overview of flower and examine floral, fruit, & inflorescence diversity – 2nd half of Chpt. 9 The Flower — What is it? The Flower — What is it? • “foliar theory” of flower - J.W. • specialized shoot = stem + von Goethe in “Attempt to Interpret leaves (folia) the Metamorphosis of Plants” (1790) • shoot is highly modified and determinate (ceased to grow) from Schleiden 1855 9 The Flower — What is it? The Flower — What is it? • developmental/evolutionary origin of the • developmental/evolutionary origin of the flower still debated flower still debated 1. Euanthial theory - (foliar theory) - single shoot, cone or strobilus anthers (male) ? ovules (female) 2. Pseudanthial theory - compound shoot or cone, different shoots “coalesce” or “condense” ? ? The Flower — What is it? The Flower — What is it? • thus, a flower is a specialized shoot that: The ‘ABC’ model of floral part identity 1. is determinate (vs. indeterminate) B 2. has a modified stem with compressed internodes A C sepals petals stamens carpels 3. possesses modified leaves with various functions, these determined by gene arrays (e.g., ABC model) 10 The Flower — What is it? The Flower — What is it? The evolution of the ‘ABC’ • thus, a flower is a specialized shoot that: model of floral part identity The Plant Cell, 2010 1. is determinate (vs. indeterminate) 2. has a modified stem with compressed internodes 3. possesses modified leaves with various functions, these determined by gene arrays (e.g., ABC model) 4. often clustered in an inflorescence (larger branch) The Flower The Flower read chpt 9 in Plant Systematics! • 1st half deals with vegetative features - we will cover in lab 2 this week • 2nd half deals with flowers/fruits - lab 3 next week 1. Peduncle: floral stalk, the stem supporting the flower; sometimes referred to as the pedicel 11 The Flower The Flower 2. Receptacle: modified floral stem or 3. Sepal: the outer whorl of leaves, axis from which arise the floral green and protective; collectively appendages or modified leaves called the calyx (CA) The Flower The Flower 4. Petal: the second whorl of leaves, 5. Perianth: collective term for Tepals if both similar or if only typically brightly colored, attracting sepals and petals (P) one reduced set (sepals) pollinators; collectively called the corolla (CO) 12 The Flower The Flower 8. Stamen: the male structure of collectively, stamens are the 6. Filament: slender stalk of the stamen supporting flower comprising filament and androecium (= ‘house of the anther; permits exsertion of anther with pollen anther males’) (A) out of flower The Flower The Flower Nuphar 7. Anther: fertile portion of stamen that dehisces to release pollen grains; composed of anther sacs • stamens can be leaf-like in primitive angiosperms! 13 The Flower The Flower Nectaries often near base of stamens - 13. Pistil: flask-shaped, female • all pistils (1 or more) are produce nectar reward for visitors structure comprising three main referred to as the gynoecium ‘ ’ who will move pollen (‘pollinators’)