Species Concept, Definitions, and Issues - PDF

chapter 3: SPECIES CONCEPT, DEFINITIONS, AND ISSUES CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  SPECIES CONCEPT Cuvier in 1829 defined as species as the assembledge descended from one another...

chapter 3: SPECIES CONCEPT, DEFINITIONS, AND ISSUES CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  SPECIES CONCEPT Cuvier in 1829 defined as species as the assembledge descended from one another or from common parents and of those who resemble one another. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  DIFFERENT SPECIES CONCEPT Biological Species Concept species based on interbreeding and reproductive isolation. Ecological Species Concept species roles in ecosystem. Phylogenetic Species Concept species based on evolutionary ancestry and genetic relationships. Monophyletic Species Concept considers species as a group of organisms sharing a common ancestor. Evolutionary Species Concept species based on their evolutionary history and future potential. Hennigan and Internodal Concepts consider species in relation to evolutionary branches(cladistics). Taxonomic Species Concepts traditional classification based on morphology and other observable traits. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  TYPOLOGICAL SPECIES CONCEPT is one of the oldest ways of classifying species. species are defined by a set of unchanging characteristics. Plato and Aristotle They believed that organisms (Ancient Greek belong to specific natural kinds Philosophers) that do not change over time CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  Linnaeus He classified species based on their morphological traits. Charles Darwin’s Theory of Evolution introduced the idea that species change over time through natural selection. Regan’s (1926) "A species is a community, or a number of related communities, whose distinctive morphological characters are, in the opinion of a competent systematist, sufficiently definite to entitle it, or them, to a specific name." CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  CRITICISM OF LINEAGE BASED SPECIES TEMPORAL ASPECT OF LINEAGES define species based on evolutionary history and splitting events. This approach is appealing because it acknowledges the continuity of evolutionary change. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  HOW TO RECOGNIZE SPECIES? Lineages that exist between splitting events (Hennigian species) will not be observable, even in principle because Lack of Unique Apomorphies Continuous Splitting Creates New Species CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  SPECIES AS INDIVIDUALS OR CLASSES CLASS it is a collection of things that share common properties no specific beginning or end CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  INDIVIDUALS are unique entities with a specific beginning and end. Ghiselin and Hull argue that species are individuals, meaning that species names refer to unique historical objects rather than broad categories CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  LINEAGE SPECIES CONCEPTS Defined species not as groups, but as lineages through time. Employed by Hennig and Simpson but with different results which lead to the creation of Hennigian Lineage Concept and Evolutionary Species Concept (ESC) CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  HENNIGIAN LINEAGE CONCEPT Also known as “cladistics species concept”, views a species as a lineage that exist between two speciation events, or between one speciation and one extinction event, emphasizing the splitting of lineages (cladogenesis). CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  EVOLUTIONARY SPECIES CONCEPT Defined a species as a lineage of ancestral-descendant populations that maintains its identity over time and space, evolving independently with its own unique evolutionary tendencies and historical fate. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science EXAMPLES OF TYPOLOGICAL OR TAXONOMIC SPECIES CONCEPT: Here are the examples of species classified using the taxonomic species concept, based on their distinct morphological traits: 1. Canis lupus (Gray Wolf) and Canis latrans (Coyote) Canis lupus is a large carnivorous mammal found in forests, tundras, and grasslands across North America, Europe, and Asia. It is highly social, living in packs. Canis latrans is a smaller, more adaptable canid found mainly in North and Central America. It thrives in a variety of habitats and is known for its opportunistic feeding behavior. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science EXAMPLES OF TYPOLOGICAL OR TAXONOMIC SPECIES CONCEPT: Here are the examples of species classified using the taxonomic species concept, based on their distinct morphological traits: 2. Felis catus (Domestic Cat) and Felis lybica (African Wildcat) Felis catus is a domesticated feline with a wide range of coat colors and patterns, found worldwide as pets and feral populations. Domestic Cat Felis lybica is a wild species native to Africa and parts of the Middle East, believed to be the ancestor of domestic cats. It has a more uniform coat and is more elusive in behavior. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines African Wildcat College Of Arts and Science BIOLOGICAL SPECIES CONCEPT Mayr (1942) popularized the “biological species concept,” (BSC) which states, “A species consists of a group of populations which replace each other geographically or ecologically and of which the neighboring ones intergrade or interbreed wherever they are in contact or which are potentially capable of doing so (with one or more populations) in those cases where contact is prevented by geographical or ecological barriers.” Or shorter: “Species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups.” With its central criterion being the easy to comprehend notion of interbreeding, the BSC remains a widely taught approach to delimiting species of contemporary, sexually reproducing organisms. It is not applicable, of course, to asexual organisms, fossils, allopatric populations, or any taxa about which we have insufficient information about their mating habits, and it suffers from numerous conceptual difficulties, not least of which is the observation that the ability to interbreed is a symplesiomorphy. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science BIOLOGICAL SPECIES CONCEPT John Ray (1686) was one of the first scientists to define species based on their ability to reproduce and maintain distinct traits through generations. Dobzhansky (1937) later emphasized that speciation occurs when gene flow between populations is restricted by barriers to interbreeding, leading to genetic isolation. Paterson (1980, 1985) provided an alternative view by arguing that species are defined not just by reproductive isolation but by their ability to recognize and select appropriate mates. However, the BSC is not applicable to asexual organisms, fossils, and many plants due to frequent hybridization, nor can it be easily tested in allopatric populations (Levin, 1979; Donoghue, 1985; Gornall, 1997). CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science BIOLOGICAL SPECIES CONCEPT The Biological Species Concept (BSC) is not applicable to certain groups of organisms and situations because its definition is based on interbreeding and reproductive isolation. If we cannot determine whether organisms can interbreed, then the BSC cannot be used to define species. Here’s why it does not work for specific cases: 1. Asexual Organisms – The BSC is based on sexual reproduction, but asexual organisms reproduce without mating (e.g., bacteria, many fungi, and some plants). Since they do not interbreed, the concept of reproductive isolation does not apply. 2. Fossils – Fossilized remains provide no direct evidence of mating behavior or reproductive compatibility. Without knowing whether extinct organisms could interbreed, we cannot classify them as species using the BSC. 3. Allopatric Populations – These are populations that live in separate geographic areas with no contact. Since they do not interact, we cannot test whether they would interbreed if they met. They might still be the same species or separate species, but the BSC does not provide a clear way to determine this. 4. Organisms with Unknown Mating Habits – If we lack data on an organism’s reproductive behavior (e.g., rare or newly discovered species), we cannot confirm whether they interbreed or are reproductively isolated, making the BSC difficult to apply. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  EXAMPLES OF BIOLOGICAL SPECIES CONCEPT: 1. Human ( Homo sapiens) 2. Dogs ( Canis l upus famil iaris ) and Wolves ( Canis l upus ) 3. Horses ( Equus ferus cabal l us ) and Donkeys ( Equus africanus asinus ) 4. Lions ( Panthera leo ) and Tigers ( Panthera tigris ) 5. Mallard Ducks ( Anas platyrhynchos ) and American Black Ducks ( Anas rubripes ) CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  CRITICISMS OCCURRED ON BIOLOGICAL SPECIES CONCEPT A multitude of criticisms has been leveled at the BSC focusing, appropriately, on the emphasis on sexual reproduction. A ga m ota xa (a s ex u a l c re at u re s) A s ex u a l s p e c i e s (a g n o m ate s) re p ro d u ce i n d e p e n d e nt l y w i t h o u t ge n et i c exc h a n ge. Ma j o r i t y of t a x a a re a s ex u a l a n d t h u s fa l l o u t s i d e t h e s co p e of B S C. Hi s to r i c a l l i fe o n Ea r t h l a c ke d s ex u a l re p ro d u c t i o n — ra i s i n g t h e q u e s t i o n : we re t h e re n o s p e c i e s? CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  CRITICISMS OCCURRED ON BIOLOGICAL SPECIES CONCEPT Op e ra t i o n a l d i f f i c u l t i e s i m m e d i ate l y a ro s e w h e re c re at u re s we re n ot sy m p at r i c. Al l o p at r i c s p e c i e s ( ge og ra p h i c a l l y s e p a rate d ) p re s e nt d i f f i c u l t i e s i n d ete r m i n i n g w h et h e r t h ey co u l d i nte r b re e d. Al l o c h ro n i c s p e c i e s (d i f fe re nt t i m e s) a l s o c a n n ot b e te s te d fo r re p ro d u c t i ve co m p at i b i l i t y. Mo r p h o l og y, b e h av i o r, a n d e co l og y b e co m e p rox i e s fo r d ete r m i n i n g s p e c i e s b o u n d a r i e s. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  CRITICISMS OCCURRED ON BIOLOGICAL SPECIES CONCEPT Hybr i di zat i on Hybri di zati on between l argel y al l opatri c taxa rai ses the i ssue of whether the resul ti ng organi sms represent one speci es or two. There i s no f i xed cri teri on for recogni zi ng speci es i n such cases, maki ng deci si ons subj ecti ve. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  CRITICISMS OCCURRED ON BIOLOGICAL SPECIES CONCEPT Emphasi s on reproducti on BSC emphasi zes reproducti ve i sol ati on as the pri mary mechani sm of speci ati on. Rosen ( 1979) demonstrated that reproducti ve compati bi l i ty coul d be pl esi omorphi c (ancestral ) , l eadi ng to paraphyl y. Speci es may be more cl osel y rel ated to members of di f ferent speci es than to thei r own. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science PHYLOGENETIC SPECIES CONCEPT(S) Starting with Donn Rosen in the late 1970s, cladistic ideas were applied to the species problem. These resulted in a series of “phylogenetic” species definitions that differed in their emphasis on monophyly and the tokogenetic relationships (Sect. 2.1.2) between parents and offspring. Unlike the BSC, reproductive com-patibility has no special place in these species concepts, but each emphasizes aspects of historical or parental patterns of relationship. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  EXAMPLES OF PHYLOGENETIC SPECIES CONCEPT(S): Here are the examples of species classified using the phylogenetic species concept (PSC): 1. African Elephant Split: Loxodonta africana ( Savanna Elephant ) and Loxodonta cyclotis (Forest Elephant) Loxodonta africana is the larger elephant species, primarily inhabiting the open savannas of Africa. Savanna Elephant Loxodonta cyclotis is smaller, with straighter tusks, and is adapted to dense forests in Central and West Africa. CEBU TECHNOLOGICAL UNIVERSITY Forest Elephant Cebu City , Philippines College Of Arts and Science EXAMPLES OF PHYLOGENETIC SPECIES CONCEPT(S): 2. Canis lupus (Gray Wolf) and Canis rufus (Red Wolf) Canis lupus is a widespread and highly variable canid found across North America, Europe, and Asia. Canis rufus is a smaller, more reddish-colored wolf native to the southeastern United States. 3. Ammospiza maritima (Seaside Sparrow) and Ammospiza nigrescens (Dusky Seaside Sparrow) Ammospiza maritima is a salt marsh sparrow species with multiple subspecies found along the U.S. Atlantic and Gulf Coasts. Ammospiza nigrescens was a darker-colored sparrow, historically found only in the marshes of Florida, but it went extinct in 1987. CEBU TECHNOLOGICAL UNIVERSITY Dusky Seaside Sparrow Cebu City , Philippines Seaside Sparrow College Of Arts and Science  AUTAPOMORPHIC/MONOPHYLETIC SPECIES CONCEPT According to Donn Eric Rosen (1979), this species concept defines a species as the smallest diagnosable monophyletic group. This means that a species is the least inclusive group of organisms that can be identified by at least one autapomorphy (a unique derived trait that distinguishes it from all other groups). Donn Eric Rosen (1929-1986) CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  CRITICISMS OCCURRED ON AUTAPOMORPHIC/MONOPHYLETIC SPECIES CONCEPT Applicability Below Species Level (The Reticulate Nature of Bisexual Taxa) The Stem or Ancestral Species Conflict CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  CRITICISMS OCCURRED ON AUTAPOMORPHIC/MONOPHYLETIC SPECIES CONCEPT (1) Applicability Below Species Level (The Reticulate Nature of Bisexual Taxa) monophyly may not apply neatly to populations within a species due to the reticulate nature (web- like genetic exchange) seen in sexually reproducing taxa. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  CRITICISMS OCCURRED ON AUTAPOMORPHIC/MONOPHYLETIC SPECIES CONCEPT (2) The Stem or Ancestral Species Conflict According to Hennig’s terminology, an ancestral or stem species cannot have apomorphies that are not share by its descendant. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  CRITICISMS OCCURRED ON AUTAPOMORPHIC/MONOPHYLETIC SPECIES CONCEPT If a clade is to be recognized as a species, its ancestor must also fit that definition. But without unique traits (apomorphies), the ancestor cannot be identified in the same way. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  EXAMPLE OF AUTAPOMORPHIC/MONOPHYLETIC SPECIES CONCEPT In a cco rd a n ce to Ro s e n’s d ef i n i t i o n to Au t a p o m o r p h i c / Mo n o p hy l et i c Sp e c i e s Co n ce pt : Mo d e r n Sn a ke s (s u b o rd e r Se r p e nte s) CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  Monoism and Pluralism Monoism Suggest that there is one true species concept that applies to all organisms Pluralism Accepts that different species concept are useful in different concept CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  Pattern and Process Pattern refers to Process defines species classifying species based on how they evolve, based only on their particularly through interbreeding and gene shared ancestry flow. (monophyly) without considering how they evolve. No single definition can fully balance both pattern and process. Some propose using "monophyly" for pattern classification and reserving "species" for evolutionary CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines processes. College Of Arts and Science  Species Nominalism Originated from William of Ockham. Argues that species are not real, natural categories but rather mere names or labels assigned by humans to groups of organisms. Nature only produces individuals and species are man made. Principles Universal - property that is possess by different organisms. (e.g., plants, algae, cyanobacteria are photosynthesizing organisms) Particular - individual instances of an organism. (e.g., dog, horse, human) CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  Example of species nominalism Gray wolf (Canis lupus ) Eastern Wolf ( Canis lycaon ) Larger in size (50-80 kg) Smaller in size (30-50 kg) Longer legs Shorter legs Wider skull Narrower skull CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  Species Nominalism According to Darwin (1859b). "At the very least, for species to be real in any sense they must first be non-arbitrary." 1. Reproductive isolation 2. Genetic distinctness According to Vrana and Wheeler (1992), species level is entirely arbitrary and not fundamentally different from higher taxa (e.g., genera, families, orders). CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science  How does species concept matter? 1. It provides a framework for studying and describing the diversity of life. 2. It defines species accurately and ensures the preservation of genetic diversity and ecosystems. 3. It provides insights on how populations evolve and diverge. CEBU TECHNOLOGICAL UNIVERSITY Cebu City , Philippines College Of Arts and Science