Lecture 10: Reproductive & Genetic Species Concepts 2022 PDF

Lecture 10: Species as Reproductive & Genetic Units 1 http://www.answering-christianity.com/p648029-sperm_fertilizing_egg-spl.jpg  Recap: introduced species concepts morphologica...

Lecture 10: Species as Reproductive & Genetic Units 1 http://www.answering-christianity.com/p648029-sperm_fertilizing_egg-spl.jpg  Recap: introduced species concepts morphological species concepts Reproductive Species concepts - emphasizes reproduction to the exclusion of all other criteria Genetic Species concepts – focus on genetic criteria in defining species 2  What controls morphology of individual organisms (= phenotype)?  Genes (= genotype) What controls morphology of the species?  Gene pool Malene Thyssen, http://freedomspalace.for http://commons.wikimedia.org/wi umotion.com/t23-the- ki/User:Malene tundra-wolf 3 How are genes passed on from one generation to the next?  reproduction What does reproduction do to the gene pool?  Changes frequency of genes What then acts on the gene pool to select for or against genes?  Natural Selection 4   It is reproduction and natural selection that causes the gene pool to change What is this change called?  EVOLUTION Changes in the gene pool (= evolution) does what to the morphology?  Changes it 5   Eventually the discontinuity in morphology and genes between species is maintained by mechanisms that restrict gene flow between diverging gene pools Once genes stop flowing between sister gene pools, what has been achieved?  Reproductive isolation What is “created” as a result of reproductive isolation?  New species 6  these genecological (= gene behaviour) processes form the basis of a group of concepts which are called biological species concepts - biospecies most widely used biological species concept is Ernst Mayr’s Isolation Species Concept = ISC 7  MAYR’S (1963) BIOLOGICAL SPECIES DEFINITION “Species are groups of interbreeding natural populations that reproductively isolated from other such groups” Tamaskan Dog By Kirsten Dieks Malene Thyssen, Wiki Creative Commons http://commons.wikimedia.org/wi ki/User:Malene 8  Susan Lynn Peterson Malene Thyssen, Wiki Creative Commons http://commons.wiki media.org/wiki/User: Malene 9  BIG PROBLEM – species that hybridize have to be sunk into one species even if morphologically distinct So what do we do in the case which follows? + =? http://www.maniacworld.com/li Bjørn Christian Tørrissen Wiki ons-vs-everything.html Creative Commons liger is a hybrid cross between a male lion (Panthera leo) and a tigress (Panthera tigris) 10 Disadvantages of the Isolation Species Concept hard to apply in reality rigorous experimentation makes them difficult to use by laypersons and non-biologists impossible to apply to fossils cannot be applied to plants which are autogamous or apomictic https://en.wikipedia.org/wiki/Asexual_reproduction 11 Disadvantages of the Isolation Species Concept does not take into account the role Pop A of natural selection in speciation??? Why?? the evolution of reproductive isolation has long been seen as the major obstacle to speciation need variation in gene pool for Pop A natural selection to act upon 12 Disadvantages of the Isolation Species Concept reproductive units are not always the same as morphological units - would mean that biological species are no longer concordant with morphological species (e.g. jelly fish) because of rampant hybridization strict application would be disastrous to botany which would have to sink thousands of good species 13 https://www.rhs.org.uk/plants/articles/misc/Kniphofia Because of the problems with Reproductive Isolation some recent concepts have abandon it as a criterion Recognition species concept Reproductive isolation is byproduct of mate recognition. Problem: can only be used in biparental, sexually reproducing organisms ( excludes plants - ouch!!!) Cohesion species concept A collection of intrinsic cohesion mechanisms keeps a species discrete and this is not solely due to reproductive isolation Biosystematic species concept Focuses on gene exchange only and ignores reproductive isolation 14  Species types emanating from Reproductive Species Concepts Multispecies Genetically coherent but may not be isolated Microspecies (or biotypes) Apomictic species in which no sexual reproduction takes place Sibling species Have similar morphology (suggesting gene exchange) but, in fact, are reproductively isolated Cryptic species Similar to sibling species but have some hidden character, often chemical/molecular, makes them distinct 15 Species as Reproductive Units Reproductive Isolation Biological Species Concept Without Isolation Recognition Species Concept Cohesion Species Concept Biosystematic Species Concept 16 Types of Species Multispecies Microspecies/ Biotypes Sibling Species Cryptic Species 17  NOTE Some countries have adopted the biological species concept as the legal definition of species Besides affecting laws governing the trade of species e.g. CITES, this has enormous consequences for conservation efforts and for economic growth 18  Species as Genetic Units What does Reproduction & Natural Selection Control? 1. Flow of genes from one generation to the next 2. Demography of genes in the gene pool  some think it is all about the genes 19  Genetic Cluster Concept deals with Mendelian Populations = widespread species in which all the populations have the potential to breed characterizes a species by its entire gene pool = Genospecies (i.e. sum of all the genes) species differ from each other in having gene pools with distinct gene clusters/ frequencies 20 A species gene pool remain distinct because of: 1. Reproductive processes 2. Ecological pressures 3. Geographical constraints 4. Behavioural traits 5. Other isolating mechanisms 21 1. Reproductive processes e.g. pre and post- zygotic isolation - Cichlid fishes – Pundamilia nyererei & Pundamilia pundamilia - in normal light females of both species prefer conspecifics males - in monochromatic light – colour differences invisible, females of both species don’t show male preference - mating behaviour – prezygotic isolation - Pg 358 Ridley (2004) 22 2. Ecological pressures https://en.wikipedia.org/wiki/Canada_lynx 23 NAO = North Atlantic Oscillation: Fluctuations in atmospheric pressure, controls strength and direction of westerly wind and storm tracks across N. Atlantic 24 3. Geographical constraints 25 4. Behavioral traits 26  Inguinal: the region of the groin or either of the lowest lateral regions of the abdomen Call duration and Panguana Inguinal patch 27 Catuaba Residuals of note duration  Genotypic Species Concept based on degree of similarity (of individuals or populations) in a small portion of their molecular RNA or DNA Techniques used include to determine similarity: - Hybridization methods (e.g. FISH) - Fingerprinting (e.g. RAPD) - Sequencing of selected genes & Genetic Barcoding the use of nucleotide sequence data has become a popular taxonomic tool http://wwwnc.cdc.gov/eid/images/03-0219-F1.jpg 28  The Use of Gene Sequences Phylogenetic tree based on gene sequences using Bayesian Inference, MP and NJ 29 30  Genetic Barcoding technique aims to identify all living species using a short standardized fast evolving DNA sequence (= barcode) proposed & utilized with success by Herbert et al. (2003) Species A Species B 31  Check following clips…………… http://www.youtube.com/watch?v=ZImiXgU 6bCk&feature=related – DNA barcoding http://www.youtube.com/watch?NR=1&v=i Os6rI2Dtbs&feature=endscreen – Dan Janzen 32  the genetic marker/gene tag needs to be: 1. Species specific 2. Fast evolving barcodes must be linked to an acceptable scientific name & species description http://3.bp.blogspot.com/-lm- 33 NzSAFehM/TeeNFQTIhJI/AAAAAAAABwc/z78jGjdwbVc/s1600/ Luoma-Barcoding-lg.gif  Animal Kingdom – the Folmer region of the cytochrome c oxidase subunit 1 [CO1], a 648-bp region, of a mitochondrial gene (mtDNA) is used Plant Kingdom is problematic but two regions are being used – rbcL & MatK (both chloroplast) Herbert et al. (2003) - technique can identify up to 98% of living organisms – successfully used in birds & butterflies 34  Genetic Barcoding can be used to distinguish cryptic species works for organism at all stages of their life- cycle e.g. insects can be used on fossils quick & cheap great potential in forensics 35  Herbert et al. (2003) suggests a limit of 2% difference in barcode sequences as a cut off point to distinguish species in animals however, this may not be fine enough for distinguishing very closely related (sister) species 36  originally conceived as a method of identification & cataloguing now become a method for finding and defining species!! THIS IS CONTROVERSIAL!!!! 37  Problems of Barcoding one species may have more than one barcode accuracy as a method for defining new species not yet established over simplifies (trivializes?) the complex phenomenon of species & speciation it is possible for two different species to have the same barcode (= convergent evolution or chance) may not be fine enough to pick-up newly diverged or diverging species 38 39  moves back to use of one character to define species – too little evidence to make scientific conclusions thousands of genes??? undermines the present system which aims at precision and accuracy of identification poor science? 40 https://www.emaze.com/@AIOLRWII/justinkeller  Conclusion Reproductive Species concepts - emphasizes reproduction in defining species Genetic Species concepts - emphasizes genetics in defining species 41