On 12/5/23 8:05 PM, Sight Reader wrote:
> On Tuesday, December 5, 2023 at 9:13:45 AM UTC-7, erik simpson wrote:
>> Abstract
>>
>> Whereas living representatives of Pseudosuchia, crocodylians, number fewer than 30 species, more than 700 pseudosuchian species are known from their 250-million-year fossil record, displaying far greater ecomorphological diversity than their extant counterparts. With a new time-calibrated tree of >500 species, we use a phylogenetic framework to reveal that pseudosuchian evolutionary history and diversification dynamics were directly shaped by the interplay of abiotic and biotic processes over hundreds of millions of years, supported by information theory analyses. Speciation, but not extinction, is correlated with higher temperatures in terrestrial and marine lineages, with high sea level associated with heightened extinction in non-marine taxa. Low lineage diversity and increased speciation in non-marine species is consistent with opportunities for niche-filling, whereas increased competition may have led to elevated extinction rates. In marine lineages, competition via increased lineage diversity appears to have driven both speciation and extinction. Decoupling speciation and extinction, in combination with ecological partitioning, reveals a more complex picture of pseudosuchian evolution than previously understood. As the number of species threatened with extinction by anthropogenic climate change continues to rise, the fossil record provides a unique window into the drivers that led to clade success and those that may ultimately lead to extinction.
>>
>> In case we were wondering, here's why there are so many more kinds of birds than crocodilians.
>
> This article has me confused over the difference between “speciation”
> and “lineage”. There are cases where they say having fewer lineages
> increased speciation. If there’s a lot of species in just a few
> lineages, would that mean a lot of these species were really similar
> because they belonged to the same few lines?
A lineage is a branch (or temporal series of branches) on a tree. The
number of lineages at any one time is estimated by slicing a
time-calibrated tree at some time horizon and counting the number of
branches. A species is the representative of a lineage existing at some
particular time.

On 12/6/23 12:43 PM, Sight Reader wrote:
> On Wednesday, December 6, 2023 at 7:14:09 AM UTC-7, John Harshman wrote:
>> On 12/5/23 8:05 PM, Sight Reader wrote:
>>> On Tuesday, December 5, 2023 at 9:13:45 AM UTC-7, erik simpson wrote:
>>>> Abstract
>>>>
>>>> Whereas living representatives of Pseudosuchia, crocodylians, number fewer than 30 species, more than 700 pseudosuchian species are known from their 250-million-year fossil record, displaying far greater ecomorphological diversity than their extant counterparts. With a new time-calibrated tree of >500 species, we use a phylogenetic framework to reveal that pseudosuchian evolutionary history and diversification dynamics were directly shaped by the interplay of abiotic and biotic processes over hundreds of millions of years, supported by information theory analyses. Speciation, but not extinction, is correlated with higher temperatures in terrestrial and marine lineages, with high sea level associated with heightened extinction in non-marine taxa. Low lineage diversity and increased speciation in non-marine species is consistent with opportunities for niche-filling, whereas increased competition may have led to elevated extinction rates. In marine lineages, competition via increased lineage diversity appears to have driven both speciation and extinction. Decoupling speciation and extinction, in combination with ecological partitioning, reveals a more complex picture of pseudosuchian evolution than previously understood. As the number of species threatened with extinction by anthropogenic climate change continues to rise, the fossil record provides a unique window into the drivers that led to clade success and those that may ultimately lead to extinction.
>>>>
>>>> In case we were wondering, here's why there are so many more kinds of birds than crocodilians.
>>>
>>> This article has me confused over the difference between “speciation”
>>> and “lineage”. There are cases where they say having fewer lineages
>>> increased speciation. If there’s a lot of species in just a few
>>> lineages, would that mean a lot of these species were really similar
>>> because they belonged to the same few lines?
>> A lineage is a branch (or temporal series of branches) on a tree. The
>> number of lineages at any one time is estimated by slicing a
>> time-calibrated tree at some time horizon and counting the number of
>> branches. A species is the representative of a lineage existing at some
>> particular time.
> Hello again and THANK YOU guys!
>
> So let me see if I can get this straight…
> 1. Is it true, then, that a particular species does NOT count as a lineage or branch of the tree?
> 2. If you had a lot of lineages, why might that reduce speciation? Would a lot of lineages mean you have a lot of diversity, meaning you’ve already filled a lot of the niches that would be empty if you didn’t have a lot of lineages?
>
> Again, thank you guys for your patience and help!
1. No, it does count, but the species is at the tip of the branch only,
and we don't know how far down that branch the species continues.
Species, in general, can't be easily extended far in time or space.
2. Yes. The idea is generally that the available niches fill up, leaving
less room for new species. Of course that depends on how many species
there are in one area, not worldwide, what paleontologists call alpha
diversity rather than gamma diversity.

On 12/6/23 3:37 PM, Sight Reader wrote:
> On Wednesday, December 6, 2023 at 3:24:30 PM UTC-7, John Harshman wrote:
>> On 12/6/23 12:43 PM, Sight Reader wrote:
>>> On Wednesday, December 6, 2023 at 7:14:09 AM UTC-7, John Harshman wrote:
>>>> On 12/5/23 8:05 PM, Sight Reader wrote:
>>>>> On Tuesday, December 5, 2023 at 9:13:45 AM UTC-7, erik simpson wrote:
>>>>>> Abstract
>>>>>>
>>>>>> Whereas living representatives of Pseudosuchia, crocodylians, number fewer than 30 species, more than 700 pseudosuchian species are known from their 250-million-year fossil record, displaying far greater ecomorphological diversity than their extant counterparts. With a new time-calibrated tree of >500 species, we use a phylogenetic framework to reveal that pseudosuchian evolutionary history and diversification dynamics were directly shaped by the interplay of abiotic and biotic processes over hundreds of millions of years, supported by information theory analyses. Speciation, but not extinction, is correlated with higher temperatures in terrestrial and marine lineages, with high sea level associated with heightened extinction in non-marine taxa. Low lineage diversity and increased speciation in non-marine species is consistent with opportunities for niche-filling, whereas increased competition may have led to elevated extinction rates. In marine lineages, competition via increased lineage diversity appears to have driven both speciation and extinction. Decoupling speciation and extinction, in combination with ecological partitioning, reveals a more complex picture of pseudosuchian evolution than previously understood. As the number of species threatened with extinction by anthropogenic climate change continues to rise, the fossil record provides a unique window into the drivers that led to clade success and those that may ultimately lead to extinction.
>>>>>>
>>>>>> In case we were wondering, here's why there are so many more kinds of birds than crocodilians.
>>>>>
>>>>> This article has me confused over the difference between “speciation”
>>>>> and “lineage”. There are cases where they say having fewer lineages
>>>>> increased speciation. If there’s a lot of species in just a few
>>>>> lineages, would that mean a lot of these species were really similar
>>>>> because they belonged to the same few lines?
>>>> A lineage is a branch (or temporal series of branches) on a tree. The
>>>> number of lineages at any one time is estimated by slicing a
>>>> time-calibrated tree at some time horizon and counting the number of
>>>> branches. A species is the representative of a lineage existing at some
>>>> particular time.
>>> Hello again and THANK YOU guys!
>>>
>>> So let me see if I can get this straight…
>>> 1. Is it true, then, that a particular species does NOT count as a lineage or branch of the tree?
>>> 2. If you had a lot of lineages, why might that reduce speciation? Would a lot of lineages mean you have a lot of diversity, meaning you’ve already filled a lot of the niches that would be empty if you didn’t have a lot of lineages?
>>>
>>> Again, thank you guys for your patience and help!
>> 1. No, it does count, but the species is at the tip of the branch only,
>> and we don't know how far down that branch the species continues.
>> Species, in general, can't be easily extended far in time or space.
>>
>> 2. Yes. The idea is generally that the available niches fill up, leaving
>> less room for new species. Of course that depends on how many species
>> there are in one area, not worldwide, what paleontologists call alpha
>> diversity rather than gamma diversity.
>
> OK, lemme see if I properly understand. The article makes it clear
> that the number of lineages is a very different thing from speciation
> rate. If speciation is the creation of new lineages, then would it
> be correct to infer that the difference between lineages and
> speciation rate is analogous to the difference between position and
> velocity - that is, speciation is the rate at which new lineages are
> being created?
Let's be clear: speciation is the process by which new species arise.
The speciation rate is the increase in number of species per unit time,
often stated in terms of the expected number of lineage splits per
lineage per unit time. Each lineage split would result in one new species.
> Thanks for your patience!