Vertebrate Biology Life History 2024 PDF

BI2CV1: Comparative Vertebrate Biol Tuesday 29th October 16:00-16:45 Life history, reproduction, and mating systems Dr Joanna Baker Evolutionary Biology Group [email protected]  What is Life History?  Life history refers to the pattern and survival an...

BI2CV1: Comparative Vertebrate Biol Tuesday 29th October 16:00-16:45 Life history, reproduction, and mating systems Dr Joanna Baker Evolutionary Biology Group [email protected]  What is Life History?  Life history refers to the pattern and survival and reproduction events during the life of an organism.  The study of life history is fundamental to biological evolution.  All organisms follow a specific life cycle with a sequence of events beginning with gestation and ending with death. This cycle and all events in between comprise the life history strategy of an organism. Lecture objectives (1/1) Lecture objectives: By the end of this lecture, you should be able to:  Identify a set of key traits that together describe the life history of an organism.  Define and describe core concepts of life history theory – including trade-offs between survival, reproduction, and growth.  Explain fundamental principles of reproductive strategy such as r- and K- selection and describe what is meant by a life history continuum.  Compare and contrast different mating systems and how they relate to reproductive success. Lecture objectives (1/1) Lecture outline: 1. Key Life History Traits Join in on your phones or laptops 2. Key concepts in Life History by going to menti.com 3. Mating Systems 4. Conclusions When you see this symbol, I will highlight further reading, questions to consider, and exercises to complete in your own time! These are not compulsory but will help you consolidate your understanding. I will upload the pdfs of any papers to Blackboard. Lecture outline (1/1) Lecture outline: 1. Key Life History Traits 2. Key concepts in Life History 3. Mating Systems 4. Conclusions Key Life History Traits (1/9) Key Life History Traits (2/9) Key Life History Traits:  Age at first reproduction  Adult body size  Number of offspring  Size of offspring  Reproductive lifespan  Number of reproductive events  Mortality Rate  Body size  Growth Rate  Post-reproductive investment (e.g. parental care) Key Life History Traits (3/9) Life scales with mass Body size is a fundamental trait and underlies most other variation. Linear relationship between a measure of interest and body mass Log- scale Key Life History Traits (4/9) Life scales with mass Key Life History Traits (5/9) Huge variability in key traits: Reproductive age is variable amongst species, and often related closely to adult survival. How old do you think each of these species are at their first reproduction? Compared to their lifespan, however… African Elephant Etruscan Shrew Most elephants give birth for the first time at between 14-15 years old Fully sexually mature at ~7 weeks of age Live for ~60-70 years. (2%) Lifespan is typically ~2 years. (0.65%) Key Life History Traits (6/9)  Size and number of offspring Litter size is an important characteristic of life history that influences many aspects of reproduction, growth, and development. Klug & Bonsall (2010), Life history and the evolution of parental care. Key Life History Traits (7/9) Evolution 64 (3).  Parental care Patterns of parental care are strikingly diverse and have evolved repeatedly. Lavaniegos-Puebla et al (2024) Who cares? Elucidating parental care evolution in extant birds. Evolution 78 (10). Key Life History Traits (8/9)  Parental care Patterns of parental care are strikingly diverse and have evolved repeatedly. Klug & Bonsall (2010), Life history and the evolution of parental care. Key Life History Traits (9/9) Evolution 64 (3). Lecture outline: 1. Key Life History Traits 2. Key concepts in Life History 3. Mating Systems 4. Conclusions Key Concepts in Life History (1/10)  Darwinian Demons A ‘Darwinian Demon’ is a hypothetical, ideal organism having optimal adaptations to all relevant environmental factors at the same time, implying unlimited access to all kind of resources and the absence of biological constraints. Fabian, D. & Flatt, T. (2012) Life History Evolution. Nature Education Key Concepts in Life History (2/10) Knowledge 3(10):24 Finite resources lead to trade-offs and strategies Key Concepts in Life History (3/10) Quality vs. Quantity (of offspring) A parent can either invest a relatively large energy budget into few (quality) offspring or invest a relatively low energy budget into many. Can anyone think of an Can anyone think of an example of an animal example of an animal with a “quantity” with a “quality” strategy? strategy? Key Concepts in Life History (4/10) Growth and survival vs. Reproduction This trade-off is all about the timing of first reproduction. Does an individual invest in their own growth or health or in producing offspring? This brings us back to the shrew and the elephant example. Key Concepts in Life History (5/10) Frequency of reproductive events Iteroparous species reproduce multiple times throughout their life. Most vertebrates are iteroparous. There are two types:  Continuous  Seasonal Key Concepts in Life History (6/10) Frequency of reproductive events Semelparous species reproduce only once in their lifetime – and then die. These species use up most of their resources to invest in this reproductive event. In Antechinus, males die of exhaustion at the end of the breeding season. In Chinook salmon, a difficult upriver migration is a huge endeavour. This results in a post “salmon run” death… …and a major feeding event for grizzly bears and bald eagles. Key Concepts in Life History (7/10) R- and K- selection strategies Classical life history theory divides the evolution of life history traits into two main strategies:  r-strategists: quantity  K-strategists: quality Key Concepts in Life History (8/10) R- and K- selection strategies Classical life history theory divides the evolution of life history traits into two main strategies:  r-strategists: quantity  K-strategists: quality Key Concepts in Life History (9/10) A Life History Continuum However, modern theory has moved away from this simple dichotomy. Species fall on a continuum. Multiple axes:  Fast-slow  Offspring size vs. offspring number  Reproduction vs. development Key Concepts in Life History (10/10) Lecture outline: 1. Key Life History Traits 2. Key concepts in Life History 3. Mating Systems 4. Conclusions Mating Systems (1/15)  Mating systems and their definitions One fundamental way species can alter their reproductive success is by changing the way they interact with other members of their own species.  Mating systems depend on the spatial distribution of resources (including mates) and life history strategy.  Polygamy (any mating system where an individual mates with multiple others) is more likely where species are patchily distributed. Mating Systems (2/15)  Mating systems and their definitions Polygamous Systems Monogamy Polygyny Polyandry Promiscuity Mating Systems (3/15) Monogamy Monogamy is common in birds (>75%) and amphibians (>60%), but less common in mammals (