Are Tenebrous Spell and Umbral Wildblooded Arcana Stack?

[Eretas]

From SirCorius on the PRPG paizo web site asked:
The descriptors for the Tenebrous Spell Metamagic Feat and the Umbral Wildblooded Arcana are fairly similar but not exact.

Tenebrous Spell (Metamagic)
You blend shadow into your spells, increasing their efficacy at the price of susceptibility to light.

Benefit: When you cast a tenebrous spell in darkness or dim light, the spell’s effective caster level and any associated save DCs are increased by 1. Any attempts at dispelling a tenebrous spell in darkness or dim light take a –2 penalty on the dispel check.

Casting a tenebrous spell in bright light is difficult, and requires a concentration check (DC 15 + twice the tenebrous spell’s effective spell level). Attempts to dispel a tenebrous spell in bright light gain a +4 bonus on the dispel check.

You cannot use this feat on spells with the light descriptor. A tenebrous spell uses up a spell Slot one level higher than the spell’s actual level, except in the case of spells with the darkness or shadow descriptor or of the illusion (shadow) subschool; this feat does not change the effective level of those spells (but still counts as using a metamagic feat for all other purposes).

Umbral Bloodline Arcana:

Whenever you cast a spell in an area of dim light or darkness, your effective caster level is increased by 1.

My question is since they both increase caster levels by 1 in dim light and darkness would they stack? I would think they would given the completely different nature of the sources and the extra weaknesses associated with tenebrous. If they don't, however, how would one get access to Umbral and Shadow Grasp metamagic without wasting a feat?

If they stack, HL didn't adjust them correctly.