#1 Why Study Herpetology

Herpetology

the branch of zoology that studies amphibians and reptiles

If amphibians and reptiles are not closely related, why are they studied together?

mainly for historical and practical reasons

What practical reasons make it convenient to study amphibians and reptiles together?

• Similar collection and preservation methods

• Similar habitats

What historical reasons led to amphibians and reptiles being grouped together?

Early biologists had limited knowledge of their biology and grouped them together based on shared ancestral vertebrate traits

• (symplesiomorphies)

Symplesiomorphies

shared ancestral traits that are retained by multiple groups

What similarities led early biologists to group amphibians and reptiles together?

• Skin lacking hair or feathers

• Presence of a distinct sinus venosus

• Incomplete separation of oxygenated and deoxygenated blood

  • (except crocodiles and birds)

• Ectothermy

How does amphibian skin differ from reptile skin?

• Amphibian skin is highly permeable to water and salts.

• Reptile skin is relatively impermeable to water and salts

Are all reptiles and amphibians ectothermic?

Most are ectothermic

• but there are important exceptions

  • pythons, some crocodilians, leatherback sea turtles, mesosaurs, dinosaurs, and birds

What proportion of vertebrate diversity is covered by herpetology?

About 25% of living vertebrate diversity

Why is herpetology important for conservation?

• Many species are threatened with extinction globally

• plays a major role in understanding biodiversity and ecological balance

  • amphibians are often very sensitive to environmental changes, offering a visible warning to humans that significant changes are taking place

What percentage of amphibians are threatened?

41%

What percentage of reptiles are threatened?

21%

Why are amphibians particularly vulnerable?

• Many live in rainforests

• Sensitive to water quality

  • desiccation:(

• Affected by chytrid fungus

Which vertebrate groups are most commonly newly described?

Reptiles first, then amphibians, mammals, and lastly birds

Why is there so much taxonomic controversy in herpetology?

• Limited data on many species

• Rapid diversification of taxa

• Poor fossil record

• Incomplete genetic data

• Difficulty distinguishing closely related species

Why is the origin of modern amphibians controversial?

We do not know whether they form a monophyletic group, and early fossils appear long after their suggested divergence from early tetrapods

Why is the origin of turtles controversial?

Turtles are very different from other reptiles, and their evolutionary origins remain unclear

• a sparse fossil record

• their unique, highly specialized body plan (the shell)

What characteristics do the amphibian and turtle origin controversies share?

• Incomplete fossil record

• Gaps in evolutionary history

• Rapid diversification

• Limited physical and genetic evidence

How does rapid diversification complicate taxonomy?

It makes it difficult to determine evolutionary relationships because many groups branch off in a short time span

Why is the fossil record problematic in herpetology?

• Fossils are rare or poorly preserved

• Small animals fossilize poorly

• Genetic data cannot be extracted from most fossils

Why can species be difficult to separate?

• Some share very similar physical traits

• Metabolism and other traits may vary widely even among closely related species

What is the “Gap” in amphibian evolution?

The earliest fossils of modern amphibians appear tens of millions of years after their suggested divergence from early tetrapods

What is controversial about Lacertilia?

It is not monophyletic

• Snakes are now understood to be a group of lizards

Why are iguanas, snakes, and birds part of evolutionary debates?

Their evolutionary origins and relationships remain complex and debated

• they represent critical, often controversial, transitions in vertebrate history

  • specifically regarding the origin of flight, the loss of limbs, and the blurring lines between reptiles and dinosaurs

Why does traditional taxonomy often not reflect evolutionary history?

It was not originally based on phylogenetic (evolutionary) relationships

• historically based on superficial morphological similarities (shared appearances) rather than shared ancestry

What causes reluctance to change taxonomic groupings?

• Attachment to traditional group names

• Disagreement among scientists

• Different analytical approaches

Who created the first phylogeny to derive taxonomies from?

Michener and Sokal

What was a limitation of the first frog phylogeny by Farris and Kluge?

It was based on very few characteristics (about six)

Why are some genus and family names controversial?

Different scientists interpret data differently and disagree on how to classify groups

How can different data types lead to different phylogenetic results?

DNA data and morphological data may support different evolutionary relationships

Why are scientists revisiting morphology?

To compare and balance conclusions drawn from DNA-based phylogenies

How can new fossils alter phylogenetic hypotheses?

They may provide transitional forms or new traits that change evolutionary interpretations

What is significant about Eocaecilia?

It may be an ancestor of caecilians

• even though it had front legs, showing limbs can be lost over evolutionary time

How can new living species change phylogenies?

Depending on whether mtDNA, nDNA, or combined data are used, relationships may be interpreted differently

• introducing new branches, refining branch points, and altering established evolutionary relationships based on updated genetic or morphological data

Why are discoveries in remote areas important?

They often reveal new taxa that reshape evolutionary trees