AASAGACITY.NET
  Knowledge is Empowering
A scoring system to define a species; an evaluation of a taxon/some taxa, using the Sensible Species Definition. 5 points between taxa makes a different species.



Geographic separation/Chance
of cross-breeding
Morphological and plumage differences Voice

Song/Calls

Habitat preference
Behaviour
including
migration
Known
DNA differences

Total Points
sp
or
subsp

Scoring 0-1-2-3 0-1-2-3 0-1-2-3 0-2-3-4 0-1-2-3 0-2-4-5

A SENSIBLE SPECIES DEFINITION (Anderson 1998 and 2012)
Species are populations that are interbreeding and which are reproductively isolated from other such populations by their reproductive isolating mechanisms.
These may include -
     geographic separation / chance of cross-breeding;
    morphological and plumage differences;
    voice;
    habitat preference;
    behavioural differences such as nest-building, social grouping or migration;
    consistent DNA differences.
Each mechanisms can be weighted according to the strength of difference from a recognised species and given a score between 0 and 5; a total of 5 would give the taxon species status.
0





1






2





3




4





5




Broad hybrid zone





e.g. Narrow and stable hybrid zone,
or good chance of interbreeding.



e.g A small chance of interbreeding.



No chance of interbreeding.

Feather tracts and/or bare parts a little different,


Feather tracts and/or bare parts noticeably different.


Feather tracts and/or bare
parts very different.

Feather tracts and/or bare
parts completely different.
Not so different voice range and/or song phrases.

Noticeably different voice range and/or song phrases,







Completely different voice range and/or song phrases.
Similar or slightly different habitat preferences.








Noticeably different habitats.







Completely different habitats.
Slightly different behaviour.





Noticeably different behaviour.




Very different behaviour.
DNA differences are barely measurable.




DNA differences are measurable.



DNA differences are larger.



DNA differences are large enough to probably have non-viable offspring.




DNA differences are so great that viable inter-breeding would be impossible.




Toucanets & Aracaris
Comparison of a Universally Accepted Species with Other Taxon such as a Subspecies
 Geographic separation/Chance
of cross-breeding

Physical differences
Voice

Song/Calls

Habitat preference

Behaviour
differences

DNA differences

Total Points
sp
or
subsp
Research -
Aulacorhynchus h. haematopygus
      Crimson-rumped Toucanet
Aulacorhynchus h. huallagae              Yellow-browed Toucanet
The known differences between these two taxon are all physical.
huallagae has -
a yellow crissum (v. a green crissum)
a yellow brow (v. a white brow)
a white line at the base of the bill (v. no bill-base line).
With these differences even a differential score of 2 is generous.
Conclusion -
While distinctive, this taxon seems to be a subspecies of
Aulacorhynchus haematopygus      Crimson-rumped Toucanet.
Research -
Selenidera maculirostris              
Spot-billed Toucanet
Selenidera gouldii                        Gould's Toucanet
Conclusion -
This is very interesting case as it is apparent that these rainforest taxa were once even more similar but have been separated by savanna habitat for quite some time. But not long enough to be different species.
Research -
Pteroglossus torquatus           Collared Aracari
Pteroglossus frantzii              Fiery Aracari
Pteroglossus sanguineus       
Stripe-billed Aracari
Pteroglossus erythropygius    Pale-mandibled Aracari
Conclusion -
Looking at the evidence one wonders why these birds were different species in the first place; they are so similar. 

0
1










0
2-3






0
1
1
2

0
2










0
1






0
1
1
1

0
0










0
0






0
0
0
0

0
0










0
0






0
0
0
0




0
0










0
0






0
0
0
0


0
0










0
0






0
0
0
0

0
3










0
3-4






0
2
2
3

sp
subsp










sp
subsp






sp
subsp
subsp
subsp